Judging on the benchmarks on the newly fall release games, I don't think any of those 300-500 dollar FX cards are worth it. Not unless you want to update drivers and patch games until Nvidia finally catches up to today's standards, I see no point in not wanting to just buy the simpler card, the 9800.
I also agree with shady, both the 5950u and 9800xt are just too much $$$ for their performance increase over their counter parts. You would be buying them for the worthless point increase in benchmark programs like 3dmark.