At 100$ it's a real bargin, that is usually what the new 060 chip cost on their own. I've seen it go for less but only once in the last 3 years so.
The MK3 is the better card with UWSCSI controller on board but as said you need the INT2 fix for A3000 (done in a minute if you have a solder iron) and it could be a bit of a problem overclocking it (not that one should, 060 is plenty fast and something you want to nurse into a long and helthy life, not a 6 month speedfreak).
I too think you should keep it to you're own machine. It's not that common to see 060 boards for sale at a resonable price so you might hate yourself for selling it. If you however decide that selling is what you want to do then put it on ebay with a starting pricetag of 250$... as long as it works perfectly it will sell itself.
