Probably shouldn't ask me, I spent $4k on my system.
You can get a good-quality receiver for around $400. My Marantz was in that range, and it has everything I need in regards to inputs/outputs, though my needs are modest compared to some.
General Guidelines from when I was shopping:
-Don't mix and match brands of speakers
-Have the forward speakers be from the same series/model line
-Rears can be of a different model line if you want to save some money. You are already compromising acoustics by going in-ceiling, and those speakers don't generally have a high fidelity workload.
-Listen to a lot of speakers if you can. A higher-end speaker shop will be better than a big-box store for learning how to listen to sound differences between speakers.
-If you are watching movies, the center speaker is probably the most important as it will handle most of the dialog
-If you primarily listen to music, the L/R towers are most important as most music is in stereo