Forum member had one here, pops and bangs and very fast too, can't remember his username now but his was 380bph? So hey're very much tunable, like any car if you have money.
If you have the money being the big one there. Unless you're willing to spend the purchase cost again, at least, you really do get no-where. These cars are cheap now. Couple grand or so. You'll be double that for a decent supercharger kit, and that MAY get you as far as 350 BHP. Unless you actually do that, you'll be looking at £500 for an exhaust, £300 for a map (maybe), and you might see 240 BHP. If you are willing to spend a couple grand on the car + 4k or so on a supercharger to get to 350 BHP, you could, instead, buy a B6 S4, with the same power, and will unlikely depreciate too much (I sold mine, sub-100k, about 4-5 years ago for that money, so they have pretty much bottomed out now). At least that'll be worth what you spent on it, rather than losing roughly half the mod value, if you can get it sold at all being so heavily modified.
For the OP though. If you are thinking about a V6 VAG, your budget wont be too far away from an early 8P 3.2 V6 A3. That's basically a mk5 R32 in disguise. You wont get the bodykit, but the engine, brakes, 4wd are all the same. They will be about 250 BHP standard, wont sound as nice as the R32 though, unless you go for a nice exhaust.