I use the Thermal Take liquid system, but it only pumps about 28 gallons per hour which isn't much. I've seen some pumps that'll push over 333 gallons per hour, but it's really up to you. With a 34-40C idle temp, I wouldn't worry about it unless you plan on overclocking. I use stock cooling on my video card, but they do make gpu cooling chips. One thing you could do is get the TT system that I have and buy a GPU waterblock. Just install the whole system except only put it on your video card.

I was very skeptical about liquid cooling myself, you know, scared that it'd leak, but so far I've only had positive effects. You're supposed to run it for 24hours outside of the case before you install it to watch for leaks. I didn't, but I haven't experienced any leaks yet.

I have a friend that put a client's computer in the back of his truck and forgot about it and a storm came along and drenced the computer. He just stuck in front of a heater for a couple of days and it worked fine, but if you have a leak while running the computer, then the water will cause a connection between wires it's not supposed to and causes the system to short out.

I wouldn't worry about it as long as you get a good system. www.xoide.com stocks water cooling sytems. I recommend putting windshield washer fluid in there and use the cooler fluid that comes with it. Another good way is to put just antifreeze (diluted) in there. With those ways, you can be assured that you have maximum cooling.