All my mp3s are at 128kbps. I've heard some people claim they can hear a quality loss, but I don't. You might get some quality loss if you start with bad source material, but I get all my music from either CD or a 320kbps download, and it sounds fine when I convert that to 128.
LC is probably right - I might notice the difference on a huge stereo system. But the biggest speakers I ever use are my studio monitors, which are only 5-inch speakers. Very high quality speakers, but not large or loud enough to bring out any difference between 192 vs 128.
So consider your needs. There's no point to higher bitrate unless you have good and large speakers. If you're a headphone and computer guy like me, 192 is more than enough (since it's more than 128, which is enough).
In terms of storage: at 128, it's about 1 MB per minute of music. Get a terabyte external drive for your music (that's what I have) and you have room for a million minutes of music. That's a few hundred thousand songs (depending on song length). Or think of it this way: almost 2 years of music.
So unless you have the gear to justify higher bitrates (or you're just a fanatical audiophile), burn those high-quality sources to CD, then convert to 128 and store that on computer. You'll get 50% more music on the same disk drive.