Sound Check...Eh.. Doesn't Really Work.

Sound check in iTunes doesn't work at all for me. I barely notice any difference. You see, I have two songs, both recorded at diff volumes and sound check doesn't make them leveled at all. One sounds really loud and the other really low and soft Both encoded at mp3 128. Now thing is, I used to use mp3 trim on the pc side which worked GREAT, it did its job excellent. On the mac side I tried mp3gain, but again, it doesn't do any thing for me. Are their better programs out there for this type of thing? Auto adjusting volume levels and making them permanent.