Water Cooling!? Dear sir, do I have news for you! You can successfully cool the GTX 590 with mere stock air cooling of the card! Your temps will be 'good' in the means of being safely below the thermal limit!
Unless you plan on going 2xGTX590's, I wouldn't bother. Even then, if your case is spacey enough for a 240mm, it probably has good enough air circulation to accommodate the 2xGTX590's w/o water cooling.
I water cooled a system out of necessity. It was a huge hassle. Today, you have the luxury of enjoying performance without excessive cooling needs. Enjoy it!
Only exception: you are a hobbist and really want to make something special. Otherwise, don't bother and enjoy your AWESOME gpu
Duly noted. I was thinking about seeing if I could get a second card come Mar/Apr, but that is still quite a ways off.
I just want the low temps for longevity, while I know it's normal, I still feel 80c is too hot.