If you have the time/skills (or at least tolerance for your own finishing skills) for a diy build I'd recommend it, that's what I've done the last several, altho I'd recommend at least duals, can be more cost effective, easier to move around, work off a single amp, etc
The speaker levels set will be a reflection of their distance to your listening position and speakers' sensitivity. Hard to know whether your surround speakers are set unusually. What are the other speakers?
A factory or full microprocessor reset in your avr should give you a clean starting point, check your manual for instructions.