Besides anyone with a little DIY knowledge does the installations themselves. for the last almost 20 yrs Ive done all my audio upgrades and installations myself.
Most difficult was my previous 1998 range rover which had a separate amp in each door and for woofer in the boot all married to the company head unit. Although the head unit was good but it was outdated so had to replace it with something that played mp3s and line input.
But once I got it working the clarion head unit was really bumping the 11 harmon kardon speakers.
Did never find a way to get my steering controls working but it was a well worth compromise in that.