Mobo advice for gaming and 3d work

Four way CrossFireX or SLI isn't really recommended, mainly due to the extra cost and small performance boost. For three way CFX/SLI boards, I suggest the MSI X58 Pro-E USB3 if you do not have a case which has eight expansion slots like the SilverStone Raven RV02, but if you have a case which does then the ASUS P6X58D-E.

MSI X58 Pro-E USB3
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

ASUS P6X58D-E - $239.99
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

As for four CFX/SLI, there are no boards that cost $300 or less which are capable of it.

For your memory, you'll want a triple-channel kit. I.e., a 3x1GB, 3x2GB, 3x4GB or 6x1GB, 6x2GB, 6x4GB etc. If you're doing professional 3D modelling then I suggest 12GB of RAM. For latencies, you'll want lower - 7-7-7-20 would be best. As for speed, you'll want 1333MHz if you're not overclocking, 1600MHz if you are.

what about the Gigabyte UD3R mobo and the ASRock X58 Deluxe3? i think they are capable of 4 way Sly/Crossfire (and cost less than the Asus mobo)? but if you say it doesn't boost performance that much than 3 way will be fine...

Im not yet doing professional 3D modeling, its more like a hobby right now.
will 6GB of RAM in this case be fine? (im also going to render a bit).

one more thing, what GPU would be better fit for my needs: ATI's HD 5850 or nvidia's GTX 470? i know for games they are about the same but for 3D work i have heard nvidia has a tendency to be better?

Thanks for helping

Lmeow, can you please suggest specific ram models? 6GB would be fine and im going to OC, what is more important lower latencies or higher frequency?

The GIGABYTE GA-X58A-UD3R is a good motherboard, one which slipped my mind while writing the post.  

6GB of RAM should be adequate for non-professional workstations. Doesn't matter though, if you feel like your RAM's holding you back, just buy another kit!  

If you don't mind spending an extra $50, the GTX 470 would be better - the only thing that I know of that nVidia would be better though would be Adobe Premiere Pro CS5 which uses the Mercury Playback Engine, that can be accelerated by CUDA supported by most modern higher end nVidia cards.

Lower latencies are more 'noticeable' than higher frequencies, but you will need higher frequencies in order to make sure that your CPU will not be held back by RAM. I'm supposing you'll do at most a 4GHz overclock, in which case this kit would be perfect, very low voltage compared to most higher end models, and low latencies too.

G.SKILL PI Series 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) - $189.99
http://www.newegg.com/Product/Product.aspx?Item=N82E168...