Dual Video Card, Two Monitors, No SLi, Few Questions.

Hello!
I have a few questions and I'm out of my depth. Major Geeks has come to my rescue before, so I thought I'd try asking a few direct questions.

1) I'm pretty sure my current 8800GTX is dying, sad to say it's only been a year and a half since I bought it, and I didn't register it so the Warranty's not valid. Ideally, since it's just starting to go bad (I only notice it on WoW, really) I'd like to use this card to power my secondary monitor (thus dedicating all the memory to it, and having it run fairly easy, since the only thing there usually is a web browser) I've updated and rolled back drivers, reseated the card, checked wattages and run it through benchmarks (though oddly enough, none of the 3DMark stuff showed any problem or artefacts on screen.) Thought it may've been the game, so I uninstalled it and reinstalled it, and same problem (though it does run smoother) Is there any other way I can test it? 'cause truth be told, I'd prefer not to buy a new card just now.
If you're interested in a screenshot, this is an example of what keeps happening. If you look in the lower right hand corner, you can see two of the icons beginning to deform. This happens fairly rapidly and all over the screen- then will suddenly quit and be fine for an hour or two. Once however, it was that bad.

2) I need a new primary card if the old one's busted beyond hope, and I think it is. Was thinkin something in the nvidia GeForce 200 series, so since the cards are so different, they can't be SLi'd. Which is fine, since I'm just keeping the old card and putting it out to pasture basically. Is it possible to run two cards in a system without SLi'ng them?

3) My Power supply is a 700w, the gtx says it needs a 300 or better to run, haven't looked at the specs on the potential new card to see what it needs. In addition to the case and proc fan, I run 3 additional 120 Scythes (though one's just on the door. Is this enough power to run both, or do I need a new PS at this rate?

Thank you for your time, and I'm sorry for the long post.