If you have no budget and you want the best this is it. This card was designed specificly for overclocking. It was just released and most likely in short supply. Its been said in the article I read that you can take this card up to and possibly over 1000mhz. The water block that comes with it is a full board block and does the job. I have 3 of the Evga GTX 580 3gb Hydro Copper 2 and if there was a way I could sell them I would to buy these new cards. Also with the full board block I have no heat issues at all and I do have mine overclocked from 772mhz to 797mhz.
You could simply buy the card you want now and then buy the waterblock for it when you are ready to go to watercooling. You can't simply buy a card with a waterblock on it and run it without a water loop...the card will overheat very quickly.
If you have any watercooling questions, post a thread with us over in the water cooling forum. Watercooling info and stickies below in my sig.
Just to give you guys an idea my 2 GTX 580s (Gigabyte OC) are under water and you need a minimum of AT LEAST 4.120 mm radiators to keep them cooler than air. I've got mine attached to 2 360 rads and they idle at 24C now. I've OCed them to 850 with no probs and could easily go higher, but keep them at stock for now.
As I have stated I have three of the Evga Hydro cCopper2 GTX 580 3gb and they are on a seperate loop by themselves with a 480 radiator (4 fans) and the idle temps are 27c to 29c and under load they go to 45c to 48c. (Call of Duty Black Opps) The three cards are clocked at 797mhz. The PNY solution seems to be bizzar at best if you do two video cards and the cpu then you have three 120mm fan/radiators to put someplace in your computer?
Honestly your best bet is to just buy a graphics card that is a reference card, or one that is not altered significantly if you plan to WC in the future. You can go to: http://www.coolingconfigurator.com/step1
And pick out the 580 you're using to see if they have a waterblock that will properly accomodate your specific card. For example the GTX 580 Super Overclock from Gigabyte is not a reference design, so you won't be able to find a water block that will fully cover all the important components, and you wouldn't want that. On the other hand, the GIGABYTE GeForce 580GTX 1536 MB (GV-N580UD-15I) (the one I have) is a reference design and you can get a waterblock for that.
Both the cards Saint 19 reccomended have full waterblocks available that I know of, so both are also good options. Just make sure that the card you choose is a reference design if you plan to watercool it in the future.