I have an old 233 ,64MB of ram. Its currently running slack 9.1 with flux box. All it does it use a web brower to connect to my mp3 server. The server uses a web based interface to download m3u play lists. Then it plays the tunes from XMMS and they go out the sound card to my stereo. It is rather slow starting X and mozilla. Would I see a speed improvement with vector 4??

Yes, I saw a serious improvement because vector doesn't eat as much RAM as Slack does. I run vector on a PI 166Mhz with 96 Mb RAM and it works great, it is at least as light as Win95. It is just a pity that I can't seem to find any lightweight browsers that support frames...
The thing you need when running linux on an old pc is RAM, you can't get enough. Once you have that, then it will work great. Vector doesn't ask much of you pc, but swapping does, so the key to a fast system is RAM! (unlike in Winblows where it will swap anyway)

I'm not sure if you would do this with an older system but I tweaked my Vectorlinux 4.0 SOHO by upgrading to XFree 4.4.0, and saw a huge improvement in overall speed. I have both Slackware 9.1 and Vectorlinux SOHO 4.0 on my desktop system and I rarely go back to my slack partition any more. I will probably remove SW once RC2 comes out for Vec.