Maximum PC

This card should run most games very well but i have been having alot of trouble with it.
I get the jitters every now and then playing games like its trying to load or save all the time.
And sometimes the FPS will drop to the teens suddenly when before it was running perfect.
The card has been tested by the manufacturer and the supplier and there is nothing wrong with the card.
I have downloaded the latest drivers from AMD, run driver sweeper and done fresh installs 3 times now to no avail.
I have tested my RAM, PSU, CPU, GPU, MOBO and my hard drives and all seems well.
I have no viruses and my registry is very clean.
What is going on? Is this card sh*t?

Games: ( tried with vsync on and off)
Condemned
Crysis 1 and 2
COD black ops
Dragon age 1

SPECS:
HAF X case
22" LED LCD
Windows 7 64-bit
700W Coolermaster PSU
M4A785TD-M EVO Motherboard
8Gb RAM @ 1333
AMD Phenom II x4 965 BE @ 3.4GHz
ASUS HD6870 DirectCU 1Gb Factory overclocked @ 915/4200
HD1: 1TB Western
HD2: 1TB Seagate

How many AMPS does the card require to run and does that psu meet the minimum AMPS required? It sounds to me like the card isn't getting enough juice.

Nasty