Hybrid Crossfire and CPUs

Is it possible to hybrid crossfire a HD4850x2 with a 790gx motherboard? Or does the crossfire already in place prevent it? If so would you recommend a HD4870 with a 790gx mobo or a hd4850x2 with a 790fx mobo?

The money saved if I got for a HD4870 with a 790GX would probaly end up getting a Phenom II X4 940 BE instead of a Phenom II X3 720 BE or would either of these be a poor choice?

And finally is the Phenom II X4 940 an am2+ only Phenom II or is it compatible in an AM3 socket as scan has it listed in a different area to other AM3 Phenom IIs. I would be using an AM2+ motherboard reguardless just want to know about upgrade paths in the future for when DDR3 is more wallet friendly.

I've been asking all these questions over the last few weeks. The general view seems to be using crossfire with the onboard graphics is a waste of time.

The 790GX boards get great reviews and have the 750 south bridge which is supposed to be the best (and newest) of the AMD sb's.

I'm also looking at the Phenom II 940, It is an AM2+ unit but, By the time AM3 is wallet friendly there will no doubt be a better cheap AM3 CPU available.
I suppose it depends on how long you intend to go between upgrades? For me I leave it long enough that I have to get a new Board,CPU and memory.

Ahhh ok thanks, and another question I forgot to ask

The DFI LANPARTY UT 790FX-M2R does not accept DDR2 8500 (only 800mhz) so would it be better to look elsewhere for a 790fx board if overclocking is in mind or just overclock the ram?

Also does the 750 southbridge make 790GXs better than 790FXs in most cases? The budget for the motherboard is about is £135 max

The 750 south bridge is available with both the 790GX and 790FX. As far as I'm aware the only difference between the FX and the GX is the crossfire(and the FX has no onboard GPU). The FX supports x16 and the GX is x8.

I've read reports about people having difficulty with 1066mhz memory with other AM2+ boards so I'm not sure what to advise for overclocking.