I think it would be best to get new cpu/mobo.
However, does your current motherboard support FX chips, and do you overclock?
I recently spent $119 at microcenter to get an FX-6300. After overclocking, my Starcraft 2 performance went from ~45 frames to ~70 frames in a typical 3v3 huge battle. But without overclocking the FX-6300, it was about tied with a heavily overclocked Phenom II. Anyway, it's an option if you want to spend about $120. Oh forgot that I also got a free motherboard from microcenter in the combo deal, but I'm just going to try to sell it along with the old PHenom II chip.
Anyway like I said it would have been better to get an intel mobo and perhaps a 3570K chip, maybe I'd get like 100 frames in my Starcraft 2 benchmark 3v3 battle replay? But I mean, my issue is I spent around $120 to get my frames from 45 to 70. Did I want to spend $400 to get my frames from 45 to 100 or 120 in starcraft 2 (I don't know what a 3570K would do in my particular replay that I used to benchmark starcraft 2, I really wish there was a built-in benchmark for that game!). I just think that maybe it's a fine compromise to just replace your CPU for very cheap, if it can tide you over for now.
Then do the ultimate upgrade to Haswell. That's my plan, spent $120 to tide me over till Haswell, *then* blow my wad on a new CPU+mobo.