Check my build please!

Your 790FX choice is not good bang for the buck. The small increase in crossfire could be more than made up by going with the faster processor instead.

X4 955:
http://www.newegg.com/Product/Prod [...] 6819103674

790GX board:
http://www.newegg.com/Product/Prod [...] &Tpk=790GX


Next up, you bought triple channel RAM. That's for Intel builds. AMD boards use dual channel.
http://www.newegg.com/Product/Prod [...] 6820227297
Your CPU will really just run these at 1333, but the price is right and you may need the speed in a later build. And no, you only need 4GB.

4870s are the best bang for the buck in crossfire builds currently I think. Especially when starting with one:
http://www.newegg.com/Product/Prod [...] 6814102801

This would be your better HD choice:
http://www.newegg.com/Product/Prod [...] 6822136074

DVD is fine.

How much do you have left for the case and PSU?

Unfortunately thats the problem with user reviews on newegg, the vast majority of users are morons who fail to do their research first. Proximon knows his stuff and looking through some of those 1 egg reviews it was early on when the bios did not support some of the AM3 processors, and people trying to put AM2+ processors in the AM3 socket.

As for the case and PSU if we assume 130 is taken for the motherboard then you need a case and PSU for ~105?

http://www.newegg.com/Product/Comb [...] mbo.197378

Should provide the power and the air flow you need for your system but you might want to get another fan if you are doing multiple graphics cards later

The memory on the graphics card isnt affected by the memory types supported by the motherboard, as long as the motherboard has the right slot and the power supply can power it the graphics card will work.

Which combo? the one i posted or a different one?

It is a better motherboard however it is a weaker graphics card and wont exhaust heat out of the case like the 4870 that Proximon linked and the difference between a 4850 and a 4870 is alot more than the difference in performance between the 790FX and 790GX chipsets.

NP Because I have a good amount of experience building and troubleshooting, I see newegg motherboard reviews a bit differently. I can often tell by the review that the fault was with the user.

You can pretty much count on any Asus "-E" type board to be a good one, at least relatively for it's chipset.

DDR3 is new to AMD builds, and so it has been a bit rocky at the start as well, as Hunter has brought up. It's a huge discount on that combo and you'll have newegg support should there be a problem and you need to return it.

Edit: ooops ya the big discount is with the X3 720