Welcome to SF!!! Sounds like you have some pretty good deals in front of you!!!
I'd have to go with the 2004 F7 . For $300 difference, less miles and reverse. you can't beat it. Plus, Reverse is a $650 option if you bought the sled new. 143 HP stock. Super easy to steer, And Hellaciously fast out of the hole.
I have not riden a Crossfire or an F8

. But The F8 is a new breed and I havn't heard much feed back yet.However I'm sure they are awsome to ride. The F7 seems to be a no brainer in a sense.
If you choose the F7 deal. MAKE SURE ALL RECALLS ARE TAKEN CARE OF FIRST. Good luck and have fun!!!!