Dude you have a good budget for the mobo
But you have to understand some thnigs
Pci Exp 2.0 is not going to change anythn and ATI vga are fully supported by pci express 1.0
so that stuck is something else probs with your driver or some other probs not a prob of your mobo
by the way dont go for intel mobos because it lacks overclocking capabilities
you best choice is to go for a P45 chipset mobo
So 1st i wonuld suggest the Asus P5Q mobo but i guess its out of stock better call and ask Baclays as well as EGS(sumtyms they might reduce the price)
2nd Choice Foxconn ELA thats 17950 @ nunet.lk its an awsum mobo with 3 pci express slots and good cooling as well
this is the mobo
http://www.foxconnchannel.com/product/Motherboards/detail_overview.aspx?ID=en-us0000398
third choice is that MSI P45 which u saw at unity
Mars is having P35 chipset and i guess its pci express 1.0
But in my opinion i strongly suggest you to go for the ELA i saw at some unity shops also