Wow, there sure are a lot of people willing to spend $100 to $200 for a K6-III+ 500!
I could possibly see spending $100 under the right conditions, but more than that???
For $70 shipped, you can get a Duron 600 that easily runs +850mhz using a $135 board, and the included heatsink and fan. You also get ATA/66+, as well as the latest chipset technology. Even a cheap board that requires a CPU mod to overclock is only $85. Even if you didn't overclock the 600, you could get a new cheap motherboard and a Duron 600 that will blow away even a K6-III+ 600, for $155.00.
I have 2 great socket 7 boards, Shuttle Hot569 and FIC 503A, and even using the 503A which supports 112mhz FSB and ATA/66, I wouldn't think of spending $100 for a K6-III+ when the new Duron's are so cheap and FAST!!! And Stable, which is something the FIC was never good at.