[antares81]

I have a 9800GX2,
Be absolutely sure that you have a huge case for this card, as it is very very large.
I had to make some modifications to my case and to my south bridge heat sinks for this card to fit. ( though I would think that your mobo would fit it)
Good ambient cooling is a must. The 9800GX2 can sometimes idle between 72C - 78C.

I would also consider getting a power supply with 1X 12V rail.(and this is up for debate)
It should be at least 32A, but most decent supplies can put out 52A and above on the 12V.

1200Watts means nothing to the video card, stability is all about stable amperage.
Several people have not been able to get the best results with multi-rail power supplies, I am one of them.

So in short, the 9800GX2 kicks ass, but you usually have to make some concessions to get it to work properly.

Interestingly enough, I had started with an 8800GTX that I had to send back to the manufacturer. They had none in stock, so was forced to send me a 9800GX2.
With the current drivers, I notice almost no difference in performance at this time.

I would use any Zalman CNPS cooler. They look ridicules but are very effective. Also pretty easy to install compared to the crappy intel stock cooler.