1. Imho, 60% of sound quality is related to room acoustics, followed by 20% for Speakers and the remaining 20% for electronics and source material.
2. Very little so far, less than 1%, I plan to purchase an SPL meter soon followed by possibly some treatment for a back corner window and back wall to clean up some imaging issues. I am willing to spend some money but WAF and overall results (perceived and actual) are concerns.
I plan to use an SPL meter and do a baseline measurement/calibration of my current setup, followed by placement layout changes for my speakers, retesting, etc. After I correlate my observations, I definitely wil factor in some purchases to improve what might be lacking in regards to room treatment. Probably be doing a DIY install since I don't think, forget that, I know I can't find someone local in my area even if was willing to pay for it.
It is easy to see why ppl would rather spend the time swapping out gear than looking after the room(s). I would say that you can spend an almost infinite amount of time on optimizing the room (if you wanted.)
Edit note: my math is bad, i just noticed my %'s didn't add up very well