Well, good mastering engineers wouldn't make it sound different in terms of the artistic choice the musician or engineer makes (and Wolf, without knowing more details, it sounds like you were the victim of a recording/mix engineer more than a mastering engineer). A good mastering engineer is sort of invisible, but the end product just sounds more there. A good mastering engineer also knows their monitoring chain and room well enough that they are not making decisions and performing drastic changes based on erroneous information. It's one of those things that, when done well, are simultaneously subtle and miraculous. A bad mastering engineer can completely butcher the material, but that's not always the fault of the engineer. A fair percentage of the butchered mastering jobs are the result of record companies demanding a loud record at the expense of sound quality (google The Loudness Wars).
Dave, you are right about keeping the files at the highest resolution possible with a bit of headroom. If you like, you could send me some files via dropbox and I can do a bit of work on them, just so you can hear what I am talking about. You are also right about the variability of cost and expertise. I tend to do it myself unless there's a budget, in which case I'll give the project to David Glasser at Airshow (he has done a number of the official GD releases, including the E72 box, the high res mastering of all the official studio releases, and pretty much all the video/movie releases in the last 6 or 7 years), Brad Sarno, who not only makes great preamps, etc., but is an excellent mastering engineer, or Steve Berson. There are many other good ones, but those are my go to guys.
My personal mastering philosophy is less is more. It shouldn't sound significantly different from the original recordings (unless there are obvious problems, but I don't hear those in your recordings). As far as guidance goes, it's pretty easily dealt with these days by sending references back and forth. In your style of music, limiting and compression should be pretty much inaudible. I just mentioned them because I know they could make the recording sound more present. If you hear it working, then it's too much.