Yes it's possible to match the volume level of MP3s, at least to a certain extent. It's not neccesarily that some CDs are recorded at lower volumes than others (although some are) but more to do with the level of dynamic range compression used during recording and mastering of the CD. You can start by using a program such as Cool Edit (www.cooledit.com) and normalize your MP3s to 100% or what is known as 0dB full scale. That will bring the peaks of the MP3 up to the maximum signal level before digital clipping and the rest of the signal levels by the same amount (in dBs). However, such normalization is usually not enough. Assuming that your MP3s are normalized to 0 dBfs, those MP3s recorded with more heavy use of dynamic range compression will have a higher average volume level than those with less dynamic range compression, thus an overall louder or hotter sound. So what you could do is either run the HiJack Kernel or the voladjust on the empeg with possible "pumping" artifacts whereby the volume of the MP3 abruptly changes during playback. Or you could apply dynamic range compression to the MP3s with a program such as Cool Edit. Although I have not used Cool Edit, I'm sure it has some sort of dynamic range compression function.

What is really needed to avoid the pumping artifacts (reported by some using the HiJack kernel) is a "softknee" compression whereby the compression gradually kicks in as it approaches the threshhold (volume level where the compession kicks in) of the compression software. I know that Hyperprism (www.arboretum.com/) supports softknee compression. Preprocessing your MP3s would of course take a lot more time than letting software on the empeg take care of it for you, but the results may be worth it. In addition, preprocessing could potentially introduce additional MP3-related artifacts due to the required conversion from MP3 to wav (for the processing) and then back to MP3 for the empeg.

Stu