dual graphics cards?

I've been off of the PC scene for quite a while now, and after desiding to build a new PC for myself I have come to the graphics card stage. I must be stuck slightly in the past, since looking at a few builds of computers have duel cards in them, none of my previous one have, and I have never previously considered this an option! So beyone the obvious 'because two is better than one' what advantages or disadvantages does having dual graphics cards have?

Btw, i am not planning on making some mega PC so this proably wont be an option for me, but its just nice to know :P

That said, i would like to hit games such as AOC and recent RTS games at top wack, so if anyone would like to suggest a good graphics card for me that would be great. I dont worry to much about the price but when its over £400 you might take some convincing me!

Cheers!

Its like have a core 2 duo processor. You have 2 rather than 1. Same idea with graphics cards. The only downside to have a dual graphics cards is that the drivers to utilitize both cards aren't very good with newer games. When new games release it seems like it takes a month or so for both the game developer to release a good patch and nvida/ati to release good solid drivers too.

So, I personally would just stick with a good single card. May I recommend the Nvidia 8800 GT 512mb. Good card for both price and performance!

Cheers for the speedy replies guys.

Most definitely i will be sticking to the single graphics card, it was more curiosity on the dual scene. I have looked at the Gforce 9800 GT2 which seems reasonably priced. Thanks for all of your recommendations, I'll check them out now!