You are coming into this at a great time as there are many options out right now for our cars. It really depends on how much power you want to make and how much you can afford.

Option 1: RS6 Turbos
AWE(GIAC), VAST, and ASP have all just released or about to release their RS6 turbo kits. These kits will put you in the 550whp range, but expect to spend anywhere from 7k-8k for parts only. Also take into account that you'll need the supporting modifications such as downpipes, clutch, flywheel, and other items.

Option 2: K04's
This is a great option as there are many tuners out there with many options. Expect numbers in the 400whp range if you do it right, and get the supporting mods again. Remember upgrading later to different turbos means another engine pull... and at the moment the tuners are not selling the RS6's turbos unless you purchase the rest of the package. Expect to spend 6k-7k to get a basic k04 setup and more with the supporting mods.

Option 3: GT28 Turbo setup

There are a few of these options out there from Vast, or ASP. Expect to pay 10-13k for these kits and numbers in the 600+ wheel horsepower range. Also expect to build the entire motor, (rods, gaskets, clutch, flywheel, manifolds, and downpipes.) This option.

You can't expect too much help with the RS6 turbo's or GT turbos locally because they are a pretty new package. K04 support is more ready. I did my own K04 install on my S4 and have been happy with it. Currently making 420 whp 420 ft/lbs. Different tuners make power different ways, and there is a ton of information out there.

Remember that if you don't install it yourself you'll probably be paying $2000-$3000 labor. Not to mention the fact that when you pull these motors apart all the little plastic pieces like to break. Factor in O2 sensor cost, EGT sensor cost, and those other items that like to fail on these cars and you'll get a pretty accurate number as far as cost goes.

phew... all that said I'm happy with K04's. Had the RS6 turbos been available when i went stage 3 a couple years ago i may have gone with them. But then again money was more of a factor back then.

join us in the southeast forum on www.audiworld.com . i go by four door there. let me know if you have more questions.