If I can be a PIA, may I suggest you encode them at nothing less than 192 kbps. Some people say 128 is cd equivalent but that's pure B.S. It's not! Far from it.

MP3's tax music, usually starting with the top & bottom frequency ranges & also possibly if you choose so joint stereo. That means loss of stereo headroom. Try listening to a cd using headphones & then listen to an mp3 encoded at 128 using headphones. If it's a song that has particular stereo separation then you will greatly notice the difference. Not to mention possible loss of bass & high frequencies. This is just a suggestion.

Songs that are encoded at 160 or above are much more attractive to others than 128 which unfortunately is the default of many mp3 encoders. eg: iTunes says below 128 is only good for talkback, yet 128 is cd quality hahaha. ie: roughly like recording on a very very cheap speak only audio tape not designed for music. Just making a suggestion so it's purely up to you. I've been thinking for a long time about making a post about unravelling the myths behind encoding music. Despite the mp2 & mp3 chitter chatter about encoding nothing compares to true listening experience.