I've installed the Pioneer and the Toshiba. I had no trouble integrating them after doing a bit of work with the IR codes & remote.

I would suggest that you let the customer buy the unit. The margin on these units is slim at best, and if there are problems with the unit or hardware failure (both are common with Tivo units) the dealer he bought the unit from is on the hook, not you. The only way you will make money on selling and installing this thing is on a T&M basis. Just a word to the wise...