Phenom II wud be better than intel config for same price. I would suggest PII X2 720 with that mobo. X3 720 does more justice to multithreaded apps than E8400/8500 even though game performance is almost close or same.
And yes, get the 4870 1GB. Its more future proof, than 4850 or 4770 even if they cud do the job as of now, but i dount if they ll make it in near future games.
4870 has higher clocks, GDDr5 and 1GB VRAm as opposed to 4850, which will push the card much ahead in upcoming games which use more than 512Mb textures.

4850 and 4870 differs mainly in memory segment.
4850: 256 bit DDR3 effective <2Ghz
4870: 256 bit GDDR5 effective 3.6Ghz
and GDDR5 oc much better too, and ive seen 4870 memory goes as high as 4.4ghz.

No need for any CF or SLi for that resolution as the fps will be more or less same [maybe some 10~20% increase] on crossfiring. If you really need that boost in performance, get a slightly better card now itself like the HD 4890 or GTX 275 for even more future proof.

I would suggest a Glacila 650AA for your rig. Simply because it has unbelievable efficiency and overloads like hell as per many reviews. It ll give enough room for oc, be in GPU or CPU or both. better vfm than HX620 if your dont mind being non modular.