[DaveSTi]

Since you have an 06 STi, the only aftermarket struts available for you are the Ohlins fixed perch ($1999). Unless you want to hack up your strut housings and put in Koni inserts, which will be cheaper than the Ohlins but require a good bit of elbow grease and test fitting. (meh.)

Lowering springs on the stock struts don't really do a good job competively. They reduce the bump travel to nothing, resulting in a very harsh ride that is deep into the bumpstops. It can be very uncomfortable to ride on the street with lowering springs on the stock struts because of the bump stop progression causing you to have a spring rate as high as 1000 lbs over the big bumps out there.

I know NASIOC loves to point people in the strut and spring combo direction, but for the STi, it really is different and I wish they'd get their collective heads out of their arses over there. The stock struts perform pretty well on the stock springs. Tokico D specs and KYB AGX aren't going to outperform them by a wide margin, and aren't even an option for the 05+ crowd. This leads you to coilovers, which in my opinion are the only way to go with the car if you're looking to be competitive.

For $1k, you can get a lot of stuff that will make the car perform better at an autocross. High spring rates, camber plates, more bump travel than the stock struts can give you, and adjustable damping. In this range you will have drawbacks with quality and valving of the strut, but they'll do a good job around cones. I like the BC Racing BR Series here vs. the Megan/Helix/PIC/etc. options due to having the largest piston diameter and vendor support. They're also not horrible on the street once you adjust them to match your tire sidewall stiffness.

Above that you can start getting into the different valving philosophies behind the different brands. Tein is a popular choice, but has a reputation for not having the most comfortable street ride. The Tein Flex are a great bang for the buck solution for someone looking to autocross the car. They also have a rep for being uncomfortable over the daily grind.

On the flipside to the Tein, Cusco (not enough adjustments) JDM offerings are the European dampers that are becoming a lot more popular over here. They're valved "better" for the roads over here (Less rebound and more digressive). In this crowd, you'll find the TiC AST coilovers, RCE T2's, KW V3's, Bilstein PSS9, Ohlins Sportlines, etc. You're now at the $2k price point and you'll have to buy your own plates separately (with the exception of the $3500 Sportlines).

For daily driver and track use, the TiC setup is probably the best of that bunch. They're single adjustable so you can't really get them setup too badly, and they offer the most bump travel available in a strut or coilover out there with the exception of some $16,000 Prodrive setup.

For more track use and daily driver, you'd want the KW V3's or RCE T2's. The T2's are upgraded V3's but still get great reviews for street use. These have some advantages over the TiC setup, mainly stainless steel construction and double adjustable. This allows you to really fine tune the damper over a broader range of spring rates and conditions. A step up in terms of difficulty for the end user, but more rewarding if you're really into your cars suspension settings. They also have almost as much bump and droop as the TiC setup.

Bilstein PSS9 are single adjustable, very comfortable, not as much bump travel or droop travel (less than my BCs), but German quality and Bilstein ride characteristics. These are a great inbetween coilover that won't beat you up on the street and will help you run quicker times. The downside is that they aren't as performance focused as either the T2's or TiC setups.

Ohlins Sportlines, think of the TiC setup, but less refined. The dyno traces show these to have a more JDM feel to them, although they've gotten great reviews (one said that they would compare to Porsches PASM in terms of feel on the street). These are also pretty highly priced vs. the competition due to our weakening dollar. People love these coilovers though, but I'm not sure on the bump travel or droop on these.

There are other differences among these options, some are inverted (Bilstein, Ohlins) and some aren't (T2's, TiC). BC offers both options. Some are dual height adjustable, some aren't. Some offer helper springs, some don't.

For swaybars, there are two competing point of views on the STi. Autocross guys love a big front bar (think 27mm on up). I love my Whiteline bar set at 29mm, even with the 8k front spring rate that I have. Other car commmunities use a large front bar as well, sometimes even larger than our 32mm BIG bars. Street and some track guys like a small or medium sized bar 22mm-26mm up front. If I were you, I'd look into the new RCE swaybars due to their range if you want to autocross or be competitive. I ran a 22mm and really didn't think it helped me much as speeds got higher. For a rear swaybar, 22mm-26mm Whiteline seems to be the standard, although the new RCE set has me thinking of making the switch over to them from Whiteline.

Perrin bars on the STi don't get used much. Fitment was a big issue with them for awhile there, then sizing came into play as people wanted bigger bars.

So to summarize this huge post:

Struts:
Ohlins fixed perch ($1999)

Springs:
RCE Black ($329)

Tophats:
Group N ($120 front, $250 rear)

Coilovers:
BC Racing BR series ($1000)
Bilstein PSS9 ($1699)
Tein Flex ($1799)
Cusco ($1899-2299)
KW V3 ($1799)
RCE T2 ($1999)
TiC SST ($2499)
Ohlins Sportlines ($3599)
Ohlins Flags ($4299)

Camber Plates:
Vorshlag ($825)
Whiteline ($389)
RCE ($429)
etc.

Sways:
Whiteline ($359 front and rear)
RCE ($360 front and rear)


My recommended street setup:

Stock tires
Camber -1.5 front and rear with 0 toe all around
Ohlins fixed perch struts
Group N tophats
RCE Blacks (higher spring rate than JDM Pinks/Prodrives with more bump travel than the RCE Yellows)
Whiteline 22-26mm front bar
Whiteline 22-26mm rear

Budget Autocross setup:
Stock tires still work great here
Camber -3 up front, -1 out back .25 toe in up front
BC Racing BR Series 5 clicks front, 3 clicks rear
Whiteline 27-29mm front bar
Whiteline 22-26mm rear bar

European Street Setup
same alignment as first street setup
Bilstein PSS9, TiC SST
same bars as first street setup

European Track Setup (autox or HPDE)
RCE T2's, TiC SST (not enough adjustability as you get more serious with track work).
I like the big bars here.


Also, don't forget to grab an X-Brace. For any level on the STi, it's worth every penny.

El Fin.