SLI gtx 460's with dual monitor (Possible solution?)

Hey guys, this is my first post ever on the forums, sorry if this is in the wrong place.

So I want to upgrade from my gtx 260 (about time huh!). I was thinking about going with a gtx 580, but I don't have the money for that so I want to run two gtx 460's. (Newegg has a November deal on them right now, nice...) However, my friend who runs this, and other people (that I have read), say that if you run SLI with two monitors, while you are ingame on your main monitor, your second monitor will go black. This is a big issue for me because I use my second monitor for ventrillo, walkthroughs, build orders, etc (I'm sure you other gamers know what I am talking about). But I had the idea that since my second monitor is never used for graphic intensive things, I could SLI my 460's and plug my main monitor into those, then use the third slot on my mobo to use my gtx 260 as a standalone gfx card and plug my second monitor into that. Who cares if my second monitor can't play crysis 2 right? Will this solve the issue because there will still be a graphics card linked to that monitor?

Are there any issues with the above setup? Please let me know!

Also on a side note, I am also buying a mobo, and I notice that most of them have two x16 slots, but if you actually have two cards in at once, they run at x8/x8... Is there a mobo that can run x16/x16 SLI? I actually have NO idea if that's even a reasonable question  . I am new to actually dealing with hardware, but I love technology in general so if I can learn something new that's always great to me - gotta start somewhere!

So please post your opinions about the top one-and-a-half questions!
Thanks for your time,
Michael A.