Got my Basso frame from this guy for a very reasonable price. I'm not sure if it's SL or SLX, but with a Record headset and a carbon fork, I wasn't about to pass it up! The Basso name comes from Marino, Renato, and Alcide Basso, three brothers who started the company in 1977 in Vicenza, Italy. Very high quality frames with a modest racing pedigree. They've always been one of the sleepers of the Italian road bike scene, which essentially translates to good values on eBay.
Here's mine: