I believe the dual 12V rails are for SLI? The Antec should definitely cut it, they make some nice power supplies. I don't remember specifically the diff between the neopower and truepower or whatever. Anybody?
If you are running the A8R-MVP with the X1900XT, it has been reported that 26 amps are suggested for stability on this particular setup. But the X1800XT with this board seems to do fine with the Antec TPII 550.
I hear the A8R32-MVP resolves this with 8-phase power design.
Lian Li PC-60plus Black Aluminum Case (w/TR-3B Black Thermometer/Fan Controller 3.5” bay)
Opteron 175 (2x 2.42 GHz, 2MB cache, Socket 939, .09 micron, E6 stepping, OSA175DAA6CD)
ThermalTake BigWaterSE 12cm liquid cooling system complete kit
Asus A8R-MVP Motherboard (ATI Radeon Xpress 200 CrossFire, socket 939, SATA2)
HiS X1800XT Graphics Card (625 MHz/700 MHz OC core/1500 Mhz/1600 MHz OC mem, Dual DL-DVI VIVO 512 MB PCIe)
ATI TV Theater 550 PRO Tuner (PCI TV and FM Tuner)
4x 512MB Corsair Micro Xpert DDR RAM (2-3-3-8-2T (spd 2-2-2-5-1T) TwinXP 1024-3200XL)
2x 74gig Western Digital Raptor Hard Drives RAID-0 (WD740GD RAID0 150gig Boot Drive)
2x 250gig Western Digital Caviar SE16 Hard Drives (WD2500KS storage and data)
Plextor 716AL Black 16x DVD/CD Burner (IDE slot loading type) Antec TP-II 550 Power Supply (550 Watt ATX12V v2.0 PSU)
Dell 2405FPW 24-inch LCD Monitor (UltraSharp Wide Aspect Flat Panel Display)
Logitech G-15 Gaming Keyboard
Logitech Cordless Optical TrackMan
Case Fans (SilenX 120mm intake, Adda 120mm exhaust blower, SilenX 92mm exhaust and SilenX 80mm Fan)
I'm currently running 1900xtx + 2 sata drives (haven't yet added my Maxtor 250gb to siggie), also DVD-RW and other DVD drive. Though I have not overclocked my rig, i have enough juice with my aerocool 550 (which i paid less then $100 ) so I believe that Antec should be good enough