If you have alot of MP3s at 128kbps is there anyway to convert them to 64 kbps?
Yes.
Besides the one given above, there are many utilities that do this. Google “convert” “bitrate” “MP3” for many results.
After installing dpPowerAmp music converter, you can convert mp3s to other bitrates with a right-click in explorer.
http://www.dbpoweramp.com/
iTunes will do this also.
Is there much quality loss in a file converted to a lower bitrate compared to one ripped directly to the lower bit rate?