From what I've read the E5200 with its 45nm transistor size is VERY overclockable, some bloke on the NCIX forums got it up to 4GHZ with a Gigabyte EG32M-S2, so you should be fine if you get the eVGA board. If you overclock it enough you should be alright for SLI, but if worse comes to worse there's the E6xxx series and the E7xxx series for not that much more.
You wouldn't see any benefit from ditching an entire card and getting a better CPU. A better CPU means a few more frames with a single video card, but by NO MEANS should you ditch a second GPU for a CPU, it will mean less frames then the first CPU and a second GPU. If you were only going for ONE GPU, then yeah I'd say go for it, but if you want to SLI, that's a different story.
Because I tend to think that factory OC'ed cards are sometimes a ripoff for what you get, I would put up your GPU for sale to see what people offer. If you get a few good ones, then sell it to the highest bidder and get two reugular 9800GTX+'s, and then just OC them yourself (it's easy). If you don't get any good enough offers, then by all means, buy a second GTX+.
The 750I board is great, but you might get it for cheaper, if you are willing to buy everything from NCIX and then pricematch from random sites you find on
Compare prices - Canada - Price Comparison - Comparison Shopping or
PriceCanada.com: Search. Compare. Buy. - Canadian Online Shopping Search and Comparison! . I would NOT go for the P5Q Pro because from what I've read, a 9800GTX+ in SLI is faster than a single GTX 260, hell, even GTX 280.
The PSU you got is alright, but you can spend $20 more and get the Corsair TX750W for $109 after $24 MIR, along with Corsair reliability (I'm unsure of BFG's PSU's quality) and peace of mind should you go to bigger and better cards in the future.
If you get this setup, the performance increases will be TREMENDOUS, especially with a second GPU, overclocked E5200, and 4GB of RAM. The AMD one you have is sort-of the same as the E5200 but not quite. It doesn't overclock as well, it's hotter, has bigger transistors (65nm process), and has less cache. The only thing your CPU has going against the E5200 is the fact that it's clocked roughly the same. But if it has less overclocking ability, and less cache, in the long run it's going to eat the E5200's 45nm-sized dirt =D