I promise, this will be my last post on this subject for at least a few days. ;)

First, you should always trust your ears over any numbers, waveform screenshots, or others’ ears. If a song or album sounds good to you, you’re done, enjoy it!
But there are a few ways you can analyze your current collection, or look up albums before you buy them:
The DR Factor - The Dynamic Range (DR) is the range between the loudest parts of a song, and the quietest parts of a song. The higher the DR number, the more dynamic the recording is, and usually, the higher the DR number, the better. BUT, just because a song or album has a low DR number, does not mean it will sound bad. Some music (like hard rock) isn’t meant to have many quiet parts, and so a lower DR number is not an immediate indicator that it will sound bad. You can look up DR values at dr.loudness-war.info (click on that for an example search for Tori Amos albums).
The Waveform - I post screenshots of waveforms from time to time to visually illustrate my points. Waveforms can be viewed in any audio editing software (Audacity is a free audio editor) and in most video editing software (all recent waveform screenshots I’ve posted are from Vegas Pro). Open up your track(s) in an editor and visually inspect the waveform. This will help confirm if something sounds off to you. But again, trust your ears, not your eyes, when it comes to music. I use screenshots to back up an argument, not make an argument.
Mastering Info/Research - Some CDs I’ll buy based solely on who mastered it. Look for the names Steve Hoffman, Barry Diament, Kevin Gray, Doug Sax, James Guthrie… you’d be pretty safe buying anything they’ve done without hearing it first, as they are known for their audiophile standards and usually REFUSE to work on any project that would require them to brickwall the master. (Read Kevin Gray’s “A Note about CD Loudness” on his company’s website)
Of course, mastering engineers aren’t exactly rock stars, so it may be difficult to find out who mastered the album you’re interested in until after you’ve purchased it and can dig in to the liner notes. In this case, I would search for or post a new thread on stevehoffman.tv asking which pressing sounds best for a specific title. Most members there own multiple masterings of their favorite albums (in fact there is an entire thread dedicated to which album each forum member owns the most different masterings of). Steve is one of the mastering engineers I mentioned above. He runs this thriving forum where music fans and audiophiles all hang out and discuss these kinds of details ad nauseum (it’s really quite fun). The forum is very active, I’m typing this at 8am and there are currently over 700 members logged in and browsing the forum.
Remasters - With few exceptions, stay away from “remasters”. The best sounding release of most albums is *usually* the first release. If you want the best sounding copy of Michael Jackson’s Thriller, track down the 35.8P-11 Japanese pressing of the CD from the mid-80s (because of how great this pressing sounds, it is expensive, everyone wants it… for a cheaper, but still GREAT sounding mastering, pick up the HDTracks.com reissue of Thriller, it’s stellar). The Postal Service reissued their only album, Give Up, this year… just buy the original 2003 CD, it’s $7 on Amazon Prime, the new remaster will just be “louder”. If you want the bonus tracks, track down the original CD singles where they were all released as b-sides, again, they will, most likely, be the best masters we’re going to get.
How do you easily find very specific pressings/masterings? Discogs. That website is amazing. I mentioned a specific Japanese CD pressing of MJ’s Thriller above and it can be confusing tracking down the pressing you want as Discogs shows 159 unique pressings of Thriller. But if you scroll through that list of pressings and click on the 35.8P-11 pressing I mentioned above, there is a Marketplace link in the right-hand sidebar where you can buy that specific pressing. Easy-peasy! It’s like eBay for audiophiles.
Finally, a note on the “volume adjusting” program you asked about. I wrote a detailed post about it here, but in short, iVolume simply adjusts the overall volume of each album in your iTunes library so all your albums are relatively the same volume when shuffling. It will NOT make brickwalled albums sound any better, it will simply turn them down, a lot, so they are the same average volume as properly mastered albums. Anyway, read that post for more info…
Glad to see so many people interested in this topic! My Adele post has over 1,000 notes, and my NIN post from a year ago on the same subject got 500 new notes in the last two days as people discuss this topic. Keep passing the info on, maybe there is some hope after all. =)