I just had a bunch of work done: Ditched a KLN 89B for a GTN 750, tossed the KMA 24 and DRE 6000 for a GMA 350c, swapped the GTX 327 for a GTX 345, added the FlightStream 510 to the GTN, and also removed KN64, KR87, KX155, Argus 7000/CE, GPS selector/annunciator panel, and relocated KX165 and HSI slaving control.
The price came to $43K, which some here will probably indicate was on the high side. However, they also removed a TON of existing wiring, rang out and tested all of the remaining wiring and antennas (and replaced one antenna and some bad coax), refurbished my old KX165, recalibrated the altitude preselector, etc... The old gear was mostly as it was from the factory, the new gear is installed so well it might be better than factory. No extraneous unused wiring, every little thing (like the panel and back-seat audio inputs) wired up exactly correctly, just really good work.
The job was done
perfectly. It was done exactly on time, exactly on budget, exactly as specified, with excellent communication throughout the process. Every feature of every box works, including the weird things that depend on interconnections between them. The price may be higher than some quotes, but it was money well spent to get the quality of work that we got.
Meanwhile, the same shop nearly always has at least one plane in their hangar that was upgraded elsewhere, with poor quality work done the first time, getting it re-done for owners who learned the hard way.
I can't recommend
Skycom Avionics highly enough. They're not a big name, but they do excellent work.