Usually MP3 radio stream streams are broadcasted at a bitrate of 128 kbps. And of course while capturing/ripping/downloading such streams you will get the files with the bitrate of the broadcast.

If you like to record any audio produced by your sound card, you may use the following freeware direct sound recording programs:
MP3DirectCut, HardDiskOGG, Audacity, Freecorder Toolbar. These programs can record sound with any bit-rate you choose even if you wanna go with mostly redundant 320 kbsp.