I had an XLS-500 in the mid-2000's. I regret selling it to fund a 4210 purchase (what a lemon of an amp!).
Great sounding amp as I recall. I had it for 2 years or so. I thought it had really strong cleans and the gain channel was very nice, though quite compressed. I was really into Megadeth at the time and that amp brought the goods to get nice and heavy. Depending on how you set the amp up, it could do the RiP/Countdown sounds pretty well, but also was capable of some pretty nice liquid leads.
My gripe with it was that I didn't feel like I could get a huge thump out of it, which in retrospect was a compression thing. It's not much of a surprise thinking back that I'm now a VHT/Fryette junky where I want my amps on the dry side. Much more of a Metallica than Megadeth amp, if you will... but that may have also been a function of my 16-17 year old self just not knowing how to set an amp up properly. I was also coming from a JCM-900 dual reverb combo, so my frame of reference was limited at that time.
The cabs are well built. I had a Horizon built Lee Jackson cab. The jacks are worth replacing (plastic crap) but otherwise nice cabinets and solid. My buddy still has that cab.
These amps have a reputation for unreliability. I didn't have issues with mine, personally. I loved rolling power tubes with it. That amp was the amp that helped me really learn and experiment on what tubes I liked with it's "self biasing" feature. I think I ended up liking 5881s most in there (go figure!) but I tried a LOT of different tube types as I recall. The 5881s seemed to coax a lot more string definition.
If the price is right, this amp may be worth a try.
