correct PSU for 7870?

Hi

I got my 7870 last week and seem to be having a few problems...

Been seeing a few graphical anomalies, in one game in particular: RW3 gets a few, most in one particular route (see pic, which does not show the flickering/alternating nature of the problem).

My PSU is OCZGXS700, which powered my 4870 ok for 3 years, and from the reviews it seems the 7870 uses a tad less power than the 4870?

I did occassionaly see an odd anomaly in RW3 with the 4870, but not as many or as frequenly as the 7870.

WinXP 32 - catalyst 12-4 drivers.

Do I need a new PSU, or is the fault somewher else?

Any help appreciated

Many thanks :)

**pic removed - see below for a video**

Here's a vid of what happens (The anomalies are much reduced when capturing a video)

http://www.youtube.com/watch?v=pVIJ0eY8dtA

hmmm - interesting. I only get these anomalies when using supersampling AA in the in-game settings....

CORRECTION: Only when using SSAA *and* FPs are more than 29 (If I use in-game setting to cap framerate at 30, I get no anomalies!)