If price really isn't a limit I'd suggest the X2 4800+, simply because it excels better in overall performance than the FX-55. Also, games will start to show up with multiple threads and the multicore processors will start to shine and leave the FX series in the dust altogether.
Looking at the market here and now however, the FX-55 is the sheer gaming monster.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w