The crown is a pro amp, designed for driving PA systems. The XLS series is class d. They will drive 2 ohms no problem. I’d still run the subs in parallel. The power at 2 ohms is 775 watts/channel. The likely reason they’re popular for subs is the also have a built in crossover. I use one in my Jam studio to drive the monitors, sounds great, I also use one to drive the speakers in my living room tv system driving Totem Sttafs. Sounds great there too. They aren’t my choice for my main system, but I use one to drive my subwoofer in my home theater and it’s excellent.
if you’re worried about age, buy a new one ($550 I think). The used ones aren’t that old though, so it’s not an issue so long as it wasn’t abused (which some are if they are used in a pro/gigging system.