1. It's not my chart. The author is Rob Sloyer.
2. Check out this thread:
http://www.m4carbine.net/showthread.php?t=33194
3. To do the old car thing:
As an unfortunate GM owner, I feel that equating DPMS with a GM is an insult!
S&W is upper midrange of AR's the top of the line - Lexus/BMW/Mercedes - are Colt, LMT, Noveske and Daniel Defense for complete rifles - in no particular order. FYI, Four seasons had MA compliant LMT's at some point, but they are priced at that level.
Bravo Company (BCM) makes very high quality uppers - if you want to attach an upper to an existing lower.