All 8800GTS 512 will perform nearly the same. If you want an overclocked version, you can overclock it your self with no problems. Any 8800GTS 512 you buy should be able to match the 9800GTX (same card reboxed under the GF9 naming) for speeds.
That being said, it will perform the same as the MSI version. If you can find a cheaper GTS 512 get it instead.
I have the exact BFG card. Best GPU I have ever owned, period.
Will overclock to 750mhz without getting hot, or any other problems what so ever.
I don't play Crysis, but I can tell you that the only single card that will do any better in Crysis is the 8800GTX. (enough to make any difference anyway) the only way to make Crysis any better than a 8800GTS is SLI'ing 2 -8800GTS's.
But will I be able play Crysis with that card on either medium or high settings?
That depends on the rest of your system and your resolution....
If it is a current system running at a reasonable resolution you should have no problem running it at medium and it should be more than playable at high. Forget about very high till the next generation cards come out, though.