to answer you'r questions,
800MHz is out and already have 4cas latencies kits for dual, i'd suggest that as a minimum and if you can get a 1066mhz get that lol [but only 4case latencies dont go for 5!!!]
Buy an X1900XT it will own any 7900GT you put against it.
Yes you should raid it.
Casing, my suggestion from exprience would be the Gigabyte 3D Aurora, I have that case and LOVE it, if not that then the Tt Shark or Kandalf which is overpriced but also is pretty nice.
Uhh, I Don't know what mobo yet, perhaps the P5W DH Deluxe ?.. thats the only one I know so far.
Cooling device, why don't you go to Petras Tech Shop and get yourself a nice water cooling kit? That place is pretty nice and every xtreme systems member has recommended that store .
I even spoke to the owner in person lol he's pretty cool....
Uhh, i dont know stuff on LCD's, someone else would have to answer you.
And the Conroe Release has already been started, your cpu is out by now but i have a feeling that in the upcoming weeks its price is going to drop alittle.