The Thermaltake watercooled cases are expensive, and sub-par compared to custom / swiftech watercooling kits. Having used one for about a year, it wasn't too bad. However, it was MUCH more expensive than an average case + air cooling, and didn't give me a ton of benefit.
The Antec P180 with the Swiftech kit doesn't look too bad, but again, don't expect revolutionary performance. The nice thing about it is the premodding and professionalism. However, the cooling is aimed more at silence than performance, and will probably only perform as well as a top-end air cooler. You always have the option of upgrading later, though.
Your absolute best bet in terms of performance-per-dollar is a decent full tower case (CoolerMaster Cosmos, Silverstone TJ-07, Thermaltake Armor, etc.) with a do-it-yourself liquid cooling loop. You will, no doubt, blow $300+ by the end, but you should have great performance if you follow the advice of the water coolers here. Learn from my mistakes - prebuilt kits aren't the way to go if you want performance; if you just want silence or ease of use, by all means go for it.