Yeah, they are nice cards and even in SLI they should pull less power than your previous cards with less heat also. But you'll be future proofed for at least 2-3 years.
Edit: Running a GTX 690 in my desktop system and this thing can drive three monitors in Nvidia Surround without any problem. I play games like Battlefield 3, Tower Wars, Dishonored, Left 4 Dead 2, Alan Wake, Skyrim. All these games were flawless in Surround maxed out (used with the Flawless Widescreen tool). This might not be the case with all games though. Some games just pull so much juice that you might need a 2nd GTX 690. But then again if you're ever going for a Surround setup, I'd recommend the 4GB cards, like 3-way SLI of GTX 670 or GTX 680 4GB.
My best friend is regretting not listening to me and getting 2 4GB 680s instead. My copy of Skyrim caps his 2GB limit and starts hammering at his FPS hehehe.