I keep meaning to transition to iVolume, but I'm also skittish with the $30 price tag and the infrequency of maintenance updates. Last update was October 2012, a month prior to a wholesale revision of iTunes, prior to the last Mac OS update, and well over a year ago (and while it claims Win 8 compatibility, that was during the period of the pre-release betas). Promising free updates doesn't mean that much when the last full revision was 5 years ago, and maintenance updates are less than once per year.
Foobar2K you just "load" the desired tracks into it and select the volume normalization from a drop down menu.
One quibble: there is no functional difference between iVolume and the free solutions beyond the automation. You're not going to get better results with iVolume, you just won't have to monkey with stuff outside of iTunes at the file level. My main reason for wanting to move to it is that my audio collection has been piecemeal normalized with mpe/AACgain one album at a time over the past 12 years. If I transition to iTunes Match, I will wind up with a nightmare of the stuff it uploads from my computer with the mp3gain tags mixed in with the stuff it matches without. An iTunes integrated solution would be much preferable, particularly since I believe the soundcheck values should be mirrored to iTunes Match.