I found this EVGA 8800 GT, with an overclock up to 700MHz, as opposed to the original 600MHz. EVGA | Multimedia Solutions The card seems like a good deal, and it's from their own website so i assume their a trustworthy retailer, and I would buy it right now, but i'm just not sure what the potential problems might be with the large overclock, which is higher than the usual 650 Mhz.
I believe EVGA offers (limited) lifetime warranty for their products.
Yes, it's safe.
A video card that is overclocked by the factory is covered by the warranty that accompanies it. EVGA's SSC edition, KO edition, and Superclocked edition are all examples of it's factory overclocked hardware (and as WhiteShark pointed out, are covered by lifetime warranties). All BFG video cards are clocked above nVidia spec. You have nothing to worry about. You would probably find it cheaper elsewhere though.
Yep, its fine.
If anything ever would happen to it from the overclock, just send it back and they will replace it.
EVGA is especially good with returns, so if you do have a problem with it, don't hesitate to call.
Is safe if you have a good PSU to handle the OC
Question. How much of a difference does a 100mhz overclock really make? How much of an FPS improvement can you look for in a 700Mhz card as opposed to a 600Mhz?
To give you an example, the 8600GTS has a 135Mhz (GPU clock) advantage over the 8600GT. The GTS averages up to 20 fps over the GT on various games (source: Tom's Hardware VGA Charts). This can be a little misleading as the GTS has a higher memory clock as well, but you get the idea. If price difference is your concern that's one thing, but if you are worried about the card failing due to the factory overclocking - DON'T BE. I have (2) EVGA 8800GTS Superclocked Edition video cards (both of course overclocked by the factory). I have had them for over 8 months with absolutely no problems - even if there were, there is always the lifetime warranty to fall back on.
Hell, I have an eVGA 7800GT KO, overclocked from the factory which I took and summarily overclocked even more on my own. Had it for what, 18 months or so now, and no problems related to the card itself.
Performance is better. How much depends as much on everything else as on the card, but frankly you can probably take the base model and overclock it to 700MHz+, but there's no guarantee. With the higher end part, you have good silicon to start with.