Amp enlightenment for a newbie…

I am setting up a new HT/music system and would like to ask for enlightenment on the purpose of an amplifier and pre-amp. Usage is HT 70%, music 30%; music preference – jazz, pop, r&b, classical, not too much into heavy stuff.

Basically, the pre-amp can be the processor or a receiver and manages the whole system. On the other hand, the amplifier is connected to the pre-amp and is used to power the speakers. Assuming my understanding is correct here are my questions:

1) What is better? A receiver (i.e. Denon 4802) plus an affordable below $1000 amp or an affordable processor and a more expensive amp?
2) Can processors/receivers without THX process THX films?
3) What is a THX amp?
4) Can you use a 2 channel amp plus a processor (i.e. rotel) for a 6 channel unit? The amp powering the front speakers and the processor supply the surround, center and subs?
5) If you have $7,500 to spend on speakers, amp and pre-amp how will you allocate?

Sorry, some of my questions might sound naïve ha ha ha.