It sounds like the file you are downloading may be in some other format.  dbpower amp will convert many different audio file types.  The Lame mp3 decoder is one of the "standard" decoders so that is not really an issue.  It may be you have the MP3 bit rate set higher than 128 and the reason it makes it larger files.  128 is the most common bitrate and produces a near wav quality file.  Or the downloaded file is in a very low bitrate (and consequently a poor quality audio file) and converting it to wav then to a "high fidelity" MP3 will give a larger file.  Also, the DVD may need the higher bitrate to decode it correctly.

If you can provide a link to the site with the download, maybe someone can determine exactly what format the file is in and give you more assistance.

Charles:

Encoding MP3s at a very low bitrate, such as 16, is an inexact science at best, as if you hadn't noticed. :) Here is a resource that might be of use to you. I suspect that if you want to listen to the MP3s on your DVD player, you're pretty much stuck with de-encoding/re-encoding with Lame, which is a plain vanilla encoder.

http://ariya.pandu.org/articles/reducing_mp3_bitrate.htm