Unless I miss hear you(what exactly is missing? the 6 pin PCI-e?).
They sell a 2 x 4 pin molex to 6 pin pci-e adapter and I would guess every card I EVER picked up came with them
That card is "just" over the 75 watt limit for no plug. so that should not be an issue.
To be honest, I had been looking at 7770's for my media center to replace its 5770. I was hoping to get a passive one, but the 650ti is looking awful tempting with lower blu-ray/dvd power consumption(and what seems to be a very quiet fan). Either way that system is rocking a 300 watt(22 amps combined 12 volt rail) power supply
That was why I wanted exact specs, because that(my media center) system was built around the 300 watt power supply(and has not pulled more then 180 watts at the wall EVER. Average gaming was about 140-160).