Speaking earnestly, I'd start with the best two channel system $5K would buy, including basic room treatments, and build from there. You might be surprised how well a two channel system with good imaging works for the occassional HT use. A good CDP with variable out would be preferable, but if a preamp were part of the package it'd have a pass through for the future processor. Next would be the addition of a processor followed by a three channel amp for the center and rear speakers. Subs and rears would follow in that order. That's what I'd do and it may or may not suit your desires.
How would you start with 5K?
I am getting started and want to get the most enjoyment for $5K in Home Theater. Music is key, but I cannot afford the best of both worlds. I live in an appartment so I don't want to over-do-it. I have about $5K to spend and I am planning to start with a Denon 3801 (new) and a pair of B&W 804's (used) and HTM-1 (used). I already have a Sony S550D and some speakers (nothing special) for the rear channel. With time I want to add an Amp, better sources and better surround speakers. What would you do?