Years ago (when I bought my D50), CMOS was considered inferior to CCD for noise reasons... now CMOS has leapfrogged over CCD. Put some fast glass in front of them and it's mind blowing how good of shots you can now get.
But... nice thing is you own the glass with your D80... look around at places like Cameta Camera (I highly recommend), B&H, and Adorama who sell Nikon Factory Refurbs of bodies for half price or less of new (and they're like-new condition, with a factory Nikon-USA warranty). It's a great way to upgrade for a fraction of the price of new... (and for the record my "refurb" D5100 had a total of 135 shots taken with it...).
Now also remember, the 5D Mark III is a "full frame" sensor... it takes in a TON of light compared to prosumer level cameras... but the newer sensors still are better than they were just a few years ago.