I also have a Lexicon MC-12 with v2 software, unbalanced (more fits my personality to have my equipment unbalanced :) Oh, and no, I'm not looking to sell.
Because I use Citation 7.1 and 5.1 amps I have no use for balanced outs, so I can't speak to that part. However, I love this unit and lexicons in general. The software is very good, the unit has tremendous flexibility, and it sounds wonderful! Now let me let you in on a wee little secret.... Okay, it isn't a secret. Dont bother upgrading to get the newer surround formats. Just get a really nice BluRay player with a good decoder and plug that sucker into the Lexicon's 5.1 inputs. Yes, you lose two channels.... Yes, that sucks. Otoh, you get to use a decade old platform for years longer without sacrificing very much. As for HDMI switching, why run HDMI thru another device when you can send it straight to your TV. If you do need switching tho, there are devices that can handle it, so again, not a big deal. And then, when the newer Lexicons come down to the $1000 range, pick up one of those, get HDMI switching and the newer DD/DTS processing, and move the old Lex to the bedroom where you'll have the baddest bedroom processor on the block. That's my plan. :)
Bt seriously, there is very little that the MC-12 cannot do and all of that can be worked around in a reasonable manner. What it does it does well and those things it still does just as well as the newest PrePros for the most part.
Of course, that's just my $.02