If you want to save some money, the ML 30XTi should perform very similarly to the 60XTi, except in deep bass, but you won't be using the deep bass advantage of the 60Xti since you will be crossing that range over to a subwoofer.
Also, since they don't look like they will be installing anything in-wall, the system setup is very easy and is something you can do yourself. Don't pay these guys to just hook up a sound system. All it is is a few speaker cables and an HDMI cable. Just follow the instructions in the
Denon manual. Make sure you get enough speaker cable and HDMI cable length for the intended system.