So I'm about to receive a ASUS P5N32-E mobo from my friend without a gpu and I was wondering if Geforce 260 will bottleneck the system. I know that the mobo is pciE 1.0 where the gpu is 2.0 so lately that was my biggest concern but after reading couple articles even one at tom's I found out that todays gpu's can't use 2.0 bandwidth and there was a slightly performance increase. So any way the mobo will run on :
Intel Core 2 Duo E6600 Conroe 2.4GHz ( probably i will overclock it to 3ghz some)
You may loose some at higher resolutions with high-max settings. However like you discovered 2.0 hasn't been pushed to the limit or near it yet. Also it's a free mobo! When you decide to upgrade you can take your GTX260 with you to a new 2.0 mobo. I think it's win win.
That depends on your budget and how comfortable you are with OCing your system. I think the GTX260 is a good price performer however I'd take a second look at the 4870HD. Depending on what games you intend to play one card or the other maybe the better choice. Also you can get a 4870HD with 1GB of GDDR as apposed to 896mb with the GTX260 for the same price. I have no idea why they didn't just give the 260 1GB. Having more GRam will also help to future proof you a bit.
but since it is a sli mobo you think i would be able to run ati because remember it is P5N32-E??? and as for the games mostly shooters like cod4, counter strike source, etc..... so which one would perform better???
Depends on the game but by and large cards in the same price bracket usually perform around the same level across the board. The GTX260 should give you great performance in everything but the most demanding games at the higher resolutions. You shouldn't have any trouble with most games at 1680X1050 with high settings. Also the nV card supports physX so in games like Mirror's Edge you'll get the added eye candy.