AMD 870 or 790FX?

Hi,

I'm planning to upgrade my current setup with the following parts:

AMD Phenom II X4 955
4GB 1333 DDR3
ATI HD5870

But I'm not sure which motherboard I should go for. I was thinking about getting one based on the new AMD 870 chipset (Asus M4A87TD EVO or Gigabyte GA-870A-UD3), but for the same amount I also have the possibility to buy a second-hand Asus Crosshair III Formula (AMD 790FX chipset) from a friend.

According to the reviews the Asus Crosshair seems to be an excellent motherboard, but it's missing the new features of the new boards based on the 870 chipset (usb3, sata2, ...).

Any ideas/suggestions?

It would entirely depend on if you plan to crossfire. The 870 boards look very nice, esp the gigabyte one but they are lacking in PCI-E lanes.
I recommend you consider the 870's with SATA3 and USB 3.0-unless crossfire is very important to you.
I had a very negative experience with the original crosshair, half of the fancy features didn't work and their customer service is horrendous. It was a $240 dollar nightmare, and I never could get an rma out of them. My pleas, emails, and rma service forms went completely ignored. Went through 3 sets of memory with that board.
I'm not saying you will have a similar experience, but if you do have a problem, then what?

Good choice, 790FX is pointless if you're not planning to CrossFireX. Besides, 870 has SATA III, some USB 3.0 and the boards are cheaper as well.

Well, for future reference, this might help (this is a basic guideline for AM3 boards):

760G - Budget, majority if not all are µATX, have integrated Radeon HD 3000 graphics, one PCI-e 16x lane.

770 - Budget, majority ATX IIRC, should have only have one PCI-e lane. Some come with two PCI-e lanes but the second one operates at 4x bandwidth, possibly resulting in bottlenecking in CrossFireX for some cards. More modern boards support SATA III and USB 3.0.

785G - Relatively budget, welll - suited for HTPC thus majority are µATX IIRC, comes with Radeon HD 4200 graphics, one PCI-e 16x lane, some has an extra PCI-e 16x lane which works at 4x like the 770 chipset.

790X - Higher end, ATX form factor supports 8x/8x CrossFireX. More modern boards support SATA III and USB 3.0.

790GX - Higher end, ATX form factor, supports 8x/8x CrossFireX, has integrated Radeon HD 3300 graphics.

790FX - Very high end, supports 16x/16x, 16x/8x/8x, 8x/8x/8x/8x CrossFireX, ATX motherboards.

870 - Budget, majority ATX IIRC, one 16x PCI-e lane, native SATA III support, some with USB 3.0.

880G - Relatively budget, mainly µATX, one 16x PCI-e lane, some come with a second at 4x, same situation with 770 chipset, native SATA III support, some with USB 3.0, has integrated Radeon HD 4250 graphics.

890GX - Higher end, ATX form factor, supports 8x/8x CrossFireX, comes with integrated Radeon HD 4290 graphics, native SATA III support, some with USB 3.0.

890FX - Highest end for AMD at the moment, all ATX form factor, supports 16x/16x, 16x/8x/8x, 8x/8x/8x/8x CrossFireX. Native SATA III support, some with USB 3.0.