Outside of the hassle of water cooling and the potential of leaking parts, I have to disagree with posts above about water cooling. It is a valid thing to do if you plan to 'silence' your system from the constant whirr of fans. I'm almost tempted to do it myself one day but I don't want to monitor the contraption.
On a side note, speed is no longer the ultimate end-game like it was in the PIII days or so. A good quad can be bought for cheap. The end game these days if to make a silent machine, yet one that still can crank out the FPS's with the best of them. That is the challenge. Water cooling is almost cheating in this regard, but it is the ultimate way to go. Large copper sinks are second.
The two types of sinks - copper and aluminum. aluminum will disapate more heat quicker than copper pound for pound. However, copper has much more mass in the same physical area and same form factor - probably 2 x the mass, so copper ultimately will be the better heat sink if they are of the same exact form factor, though it will weigh twice as much. Copper will also take longer to heat up - think large iron skillet vs small frying pan. So quick changes in temp will be ironed out as an average where the aluminum could theoretically overheat you component under the same conditions. Copper = less spikes.
A site you must visit to learn of quiet parts:
http://www.silentpcreview.com/
Those guys will teach you the best of the best for making a silent rig. Full MP3's on the sound outputs from fans to PSU's. You will be able to tell in advance if a PSU or fan will annoy you prior to putting it in your rig.
As for video card - NVidia is no longer and option this year. They are out of the game till some time next year.
As for CPU - that is the crap shoot. i7 or 955. Both work. Both have their pluses and minuses if you are talking the 920 vs the 955. If you are talking a faster i7, then the i7 will be the clear winner with the real drawback being a crazy price tag. What does the i7 965 go for these days? $1000 just for a desktop CPU? That is just wrong. It is not even a server CPU where I could understand the price tag. This is for the person willing to pay the money for a part that probably is just a clocked up 920.
Remember, Intel is usually not out for the customer, but more out for the profit. They do not have your best interest in mind. So maybe it is a moral thing with you. If not, buy what you want.
-S