Cost me $48K in 2004/5 to do the panel upgrade on a 33-35 with a GNS530 and GPSS. Already had the STECH.
Used the Beryl D'Shannon kit. Gardner Avionics in Peachtree City did an excellent job. Had to gut and re-wire everything, new breakers, etc....
My price would not be the same as yours. We did some custom work (lower breaker panel like a King Air, redundant electric vacuum instruments, etc...)
http://www.gardneraviation.com/
http://www.beryldshannon.com/products/panel.htm
As you know, there are issues with getting the STC for the GPS in these Beech panels. We had to install remote annunciator panels/switchlights because the Beech radio stack is too far to the right for Certification. The D'Shannon panel has radio placement close, if not identical to, the newer Beech's panel placement.
Gardner has done a bunch of these now and we were probably just a little more recent on the learning curve with the FSDO back when we got all the mods to my airplane approved.
I liked the panel a lot. It drew a crowd everywhere the airplane went (also had Top Prop conversion, 3/4 Speed Slope Glass, Speed Mods, Factory Re-Man, and nice paint) The free floating panel did not work as well as advertised. It seemed to amplify vibrations. The beech isolation mounts just function better and look like heavier duty parts.
Are you a member of ABS? Lots of good information if you call Tom, or one of their Tech Reps. The American Bonanza Society is a great organization to help keep these airplanes going.