If you need a $200 card now, obviously the 9800 Pro is it. Blows away 5700U and 5900XT. But upgrading from either to a 9800 pro isn't wise now unless you have use for the spare card now.
But if you can get by with your card and wait for this 6600GT and X700 to come out in AGP, that's a smart choice. Just be prepared to wait a while. IMHO, mid october is a best case scenario. I'd guess you should be prepared to wait until late November as officially AGP versions haven't been announced even.
ABIT IS7, P4 2.6C, 1GB Corsair XMS 4000 Pro Series, Radeon 9800 Pro, Santa Cruz, TruePower 430watt