Well, the AGP on that board plugs into regular old PCI (NOT PCI-E), as it is not native AGP. This means that you WILL get a performance hit if you use your 9800Pro and that board together. And as others have said, having both DDR and DDR2 as well as AGP and PCI-E means that the company has made some compromises. The company, PC-Chips, also sucks ass. My uncle had one of their boards, and as soon as he added a real sound card (an SB Live!), the whole thing became unstable, and continued to be until he got a new setup (it wasn't a power issue, as he had an Antec 400W PSU).
Long story short: look for another mobo.