Give whoever you are considering to Master your album/project just one track/song of yours to Master.
Then listen to it on the best system available to you.
You should clearly hear every detail on the original mix much better and be already thinking about making tweaks to your original mix...
Keith Rogers inspired me to take a little time for a "Match EQ" experiment. Thanks Keith.
After PDX Smitty asked about using a non factory matched, but identical model microphone with his first I thought this might shed some light on what is possible?
I know "Match Eq" is available on Logic...