Another +1 for LAME. You can harness the latest version of LAME encoder with various programs. Several windows interfaces available, like Razorlame for one, among others:
http://www.dors.de/razorlame/index.php I've used an incredible program for several years for all audio format needs. dBpoweramp.
https://www.dbpoweramp.com/ The mps encoder craps out after a month if you don't register ($30 or so?), but a pervasive converter being constantly updated with new codecs available for free. Freeware version allows all other audio conversion plugs.
Another advice if you go with an encoder or program needing the LAME dll file...
Place the most current LAME.dll in the directory with the program's exe file. This will override any older preferences stashed in the windows system directory.
Note also that dBpoweramp has LAME encorporated into the program itself, so local override doesn't happen if you dump in a more recent version of LAME with the exe file. My feeling, for mp3 level stuff, we've come far enough that 3.9 and up doesn't give any more benefit except maybe on paper specs. Nothing you can remotely hear any difference.
Free approach in my opinion is to download dBpoweramp. Accept the freeware limitation of a month demise of the mp3 codec.
Use razorlame or winLAME to fill the gap for mp3. WinLAME download at: Can't get the home page. Hope they are still alive...
http://www.softpedia.com/get/Multimedia/Audio/Audio-CD-Rippers-Encoders/winLAME.shtml These programs will accept the latest LAME dll codec.
Maybe superstition, but don't trust Sonar, Reaper to give me control over the conversion. I always save a rendered project to a stereo wave, then use external programs to do the conversion. Side note, OGG format is way superior lossy protocol to mp3 if storage space is an issue. dBpoweramp comes with the most current OGG codec.
John