Is there a .WMA file reducing program cause Tunebite's files are too large?

I’m using Tunebite 2.1 to record a number of long plain voice lecture audio files. They are in the (.WMA) Windows Media Audio 9 format at 4kbps, 8khz and mono. It sounds incredibly clear at those low settings and each file is around 15 megabytes.

Tunebite 2.1 does not seem to allow mono and the lowest setting for the .wma format is 32kbps and that does not sound good giving a kind of slurred lispy metallic sound. So I am using the 64kbps setting in stereo since there is no mono option. (I haven't tried the 48kbs setting). As a result at 64kbps, my original 15 megabyte file turns into approximately a 200 megabyte file.

If I use the mp3 format at the same kbps with no option for mono, I get even bigger file sizes -- I think it was closer to 300 megabytes and the quality seems to be worse at the low end kbps like 64kbps. So I think I will stick with the .wma format.

As I have about 30 of these 15 meg files to convert, it adds a lot of unnecessary file space. And it would be nice to store the whole collection on one or two CDs.

 It's not really such a big deal but it would be nice to know how to somehow keep the file size small with good quality.

 Could there be some kind of .wma program that could reduce the 64kbps, stereo to 4 or 8kpbs mono (like the original) without damaging the quality?

If they sound ok in the wma format I’d just stick with it.