My .02 cents:
Unless you play competitively in games....5.1 sound is a throwback. I used to have 5.1 sound but because my desk and monitor are somewhat kitty-corner, the sound fields were always wrong, so I just went back to 2.0 at my desk and I don' t miss 5.1 at all. Given a choice, I'd choose the 3D visuals...if you are into that sort of thing. Gaming and 3D for me, don't mix for anything fast-paced......I find myself not being immersed in the game, but rather being immersed in all the cool bits (and sadly, all the flaws) that 3D introduces into gaming, but your mileage may vary.
Just as an aside, does your computer or motherboard offer up Coax or TOSLINK output for 5.1 Dolby Digital/DTS streams? If so, you can use DVI/HDMI to carry the picture and the optical options to carry your sound? Your games won't flow natively in 5.1 but you can turn on the fanciest version of Dolby Pro Logic that is offered up by your receiver and do faux 5.1 sound that way.....or get a separate sound card that does Dolby Digital Live conversion and output directly in 5.1 to your receiver......
Xbox Live / PS3 / Steam: HeadRusch1
Keeping the world safe from the evil antics of Bernie Tanaka and Mel Fujitsu since 1986