Hi Im looking to buy two GPU's and wanting to spend $150-$250 each. I was looking into buying two GTX 660's but I was not for sure.
Here are my current specs on my desktops
MOBO: MSI 970A-G48
PSU: 550w ( ATM im upgrading it to a 850-875watt)
HDD: 1TB WD blue
SSD: 120gb PNY
OS: Windows 7 ultimate 64-bit
GPU: GTX 460 (looking to upgrading this)
For that price range if you can find a GTX760, it is considered to be the best GPU at that price point with performance similar to the HD 7950 and GTX 670.
Else the r9 270 or r9 270x are a good (and cheaper) option; the 270 is essentially the same as the 270x (same amount of shaders, texture units, and compute units) but the 270x has faster clock speeds.
All these card will be sufficient at gaming at 1080p and for the GTX 760 and R9 270x, gaming will be fluent maxed out with AA and/or AF depending on the game.
Its not always a good idea to go SLI right off the bat as it leaves you no room to upgrade in the future should this setup be insufficient (and the GTX 660 is an aging card) better to buy a good GPU and either add on another later or just swap it out entirely.
If that is the case consider display port since you can daisy chain multiply monitors (if your monitors support both display port or daisy chaining). If you really must have 5 monitors (and display port is not supported) then finding a card that sports a lot of display connectors may be a solution (and may take some time) else SLI'ing may be an option (as a last resort).