I have read all of the definitions for each measurement, but what are the most important things I need to know regarding these as a user/shopping for mids and tweeters? Is there a guide for old school dummies trying to catch up with the times? I read somewhere that for powerful midrange, you should look for an Fs between 50-100Hz, closer to 50 is better, and Qts between .35 and .50, closer to .35 is better...

Is this just common knowledge, or is there something to this observation?
What would the best parameters to look for in tweeters? Subs?
What about the overlap in Hertz for your whole system? If the subs work say 35-75, then midwoofers from 65-100, then mids from 90-3500, then tweeters from 2500-25k, would this be a perfect system?

I know this is probably a silly guess, but I'm just trying to make the best educated guess on which pieces to buy for my system without being able to listen to any piece until it's all installed. What do you guys look for when you are analyzing your next piece for your system? Mostly the reputation of the company, recommendations from friends or people on here, or the actual number that you see on the spec sheets and graphs that the companies provide (I would assume these can be manipulated).

Thank you for any and all feedback! You guys are helping me immensely as I try to catch up...