Yes, they need pcie connectors.
7770: 500W recommended, but less might do. 6 pin 75W connector is needed.
7750: 400W recommended, again you could scrape by with less. no extra connectors is nice, though.
7850: same pwr reqs as 7770,
7780 does not exist. you may have meant these.
ok first I meant 7850 (not 7780) and second; my power supply is 500 WATT it sais that its got a continues rating of 400 WATT however I emailed Thermaltake and they said it will run at 450 WATT comfortably BUT everybody on the forums say 300-350 WATTS I don't understand; I looked on the side of the PSU itself, its got a rating of 400 WATT, max output of 500 WATT PLEASE TELL ME EXACTLY WHAT THIS IS!!
DC OUTPUT +3.3V +5V1 +12V1 +12V2 -12V +5VSB
Max Output Current 25A 28A 14A 15A 0.3A 2.0A
Min Output Current 0.5A 0.3A 1.0A 1.0A 0A 0A
PSU specs ^ (from website)