If I remember correctly, this is the SL-2000. From the spec that are listed, it is based on the Via 82C597AT chipset, which was suppose to limit it to 66 MHZ bus. The XL-200 has the VT82C598MVP chipset which allows for 100 MHZ bus. Kind of odd as the SL-2000 were only suppose to be upgradeable to a 400 MHZ CPU, but the seller is listing a 500 MHZ CPU in this one. Perhaps undocumented jumper settings.
If they still have them, you can get the pre-upgraded unites directly at http://www.emulatorshop.com for about the same price (if you miss the auction). Last time I looked, they were selling the XL-2000 models, which is better since it has the 100MHZ bus. Of course, you will have to upgrade it yourself.
NO, I do not work for emulatorshop.com, nor have I ever bought from them before so I have no experience good or bad with them. Although their web site has been posted here many a times, so most likely others here may have done business with them before.