Which 4800 for me?

I'm using a 19x12 monitor with 4GB ram and a Phenom 9750 sitting in a K9a2 platinum. I have an overkill PSU from an old rig (A "Quadfather"...lol), so that's no worry for multiple cards.

I play every game I can get my hands on - Bioshock, SupCom, TF2 etc. I wasn't planning on getting a new card since I have 2 3870s in CF, but a friend made me an (unsolicited) offer for them that I can't refuse...

This is my shortlist of possible options
1)2x 4850 ---- $400
2)1x 4870 ---- $300
3)2x 4870 ---- $600

Should I go for the 4870 and possible CF at a later date or grab 2 4850s and not worry about it?

What do you guys think? Also I was new to ATi cards when I got the 3870s. I went with the "Diamond" brand then, but I don't know if it's like nVidia where one vendor (eVGA) is far superior. If VisionTek is any good let me know because I have like $120 in half used gift cards and reward zone money at best buy.

Yeah anything above 2 cards gets bottlenecked by the CPU, because it has to feed 3 or 4 cards simultaneously instead of just 1 or 2.

I'd take 1 4870 now and CF it with a 4870X2 later on, depending on how well that scales. If it turns out to scale really badly you can just stick another 4870 in.

Keep in mind you'll need 4 6-pin PCIe connectors to CF 4870's.

^ no you don't they are crap... look at vegas for example =( never getting ports again