Caution longish post:

Its actually quite tough for car audio installers/suppliers at the moment. The like of Car Audio Direct and other websites mean we buy Head Units at lower and lower prices. There little enough margin in a HU sale anyway. Big stereo installs dont make money either because of the man hours involved in all that fabrication and trimming etc. SO its tough to differentiate yourself from the crowd.

If you are after just a HU and some Custom fit speakers, buy from the web and DIY it. If you want an audio system properly matched, set up custom installed and trimmed and tuned to your cars interior, I'd say using a supplier like Prestige or similar is a good way to go.

Many years ago I discussed this with the guys who owned ABC in Newbury, one or two of you may remember this shop perhaps, they were often breaking new ground in the soundoff scene (this would be around 1993-1998) with Pete's MR2 they competed in the pro category (and later expert). The car had dash mounted speakers that looked factory, door builds and sub enclosures behind the seats. they manufactured a steering wheel control for the whole head unit when such things didnt really exist using a custom designed and built touch panel. The quality of work was awesome.

I was very sad when the shop closed, it was due to the fact that there was very little margin in car audio even then. Now with internet retailers its worse still.

I dont know the guys at Prestige (some of the installers went to work for the distributor BBG I think) but not everyone is trying to rip you off, sometimes the people just have overheads and are trying to make a living. Sometimes you pay a little more you get a lot more. Pay the least and you always get the least, at least thats been my experience.