i think the issue isnt the fact the work well enough in a diy environment im sure they do. But for little or no more there are far far supiriour systems available. All id say is why by a product designed to be easy as oppossed to one that designed to do a set job as its main objective. DO yourself a favour and look at the decent pro systems you can buy and still install yourself if you want.
James
programming of part set groups is an installer function, you wont find it in the user manual. But im not sure if the xl supported part sets. The xm didnt
i think that if we all went back to our 1st 10 installs we would be amazed we are still at it now!!!. Plus you will remeber how proud of them you were. I remember my first install like it was yesterday and thought it was awesome. Now im technical manager i would make the engineer in question re do it lol