Fair point, any suggestions that makes my life easier are welcome.When you consider that humans can barely detect a difference of 3db and that represents a 50% change in power, you have to realize 0.1% precision isn't necessary. Personally, I'd settle for 1% and still get called dirty names by a, "real" engineer.
I have been looking at powering options and would prefer to drive this using a DC power brick as I rather not mess with transformers fed from 240V. How much of a pain would it be to get +/-12v to the opamps that way? After all everything seems to be powered from +5v DC nowadays, however Google isn't very helpful in finding good examples to copy.