Right now I have an Asus 24 Inch Monitor and Only have enough space to use two portait monitors.

I would have to get another GPU for SLI, but want to keep it under $500 if thats possible. Any ideas on what monitors I should get?

Nvidia technically doesn't have Eyefinity, it has "Nvidia Surround".

Will it still work the same? 

pretty much... surround performance probably won't be that great wit 560ti's tho