i made a user just for you,
i have
Mobo: Asus P5N32-SLI SE Deluxe
Chipset: NForce4 SLI 16X Intel Edition
CPU: Intel Core 2 Duo E6600 @ 2.4 GHz
GPU: nVidia, XFX GeForce 8600GTS XXX X2 SLI 16X
PSU: Thermaltake Toughpower 650W
HDD: 2x Western Digital, Serial ( ATA ) 2 320GB
Memory: X2 Corsair XMS2 1GB TWIN2X1024-6400C4PRO 800Mhz
OS: Microsoft Windows Vista Ultimate 32bit X86
and running Assassins creed at 60fps on dx9 full graphics
and running at 25-50fps on dx10 full graphics
your rig is better then mine, it will work just fine!
i thought i wouldn't get high fps at dx10 with highest graphics but i did, (because the SLI...) i have framedrops to 25 but avrg of 40fps dx10 and 60fps at dx9
by the way, it's all about the forceware settings, AA (2x-16x) and Super\Multi sampeling