jrd, I've not heard any of the ASL integrated amps, but I do have a pair of Explorer 805s, 50Watt SETs powered with an 805. I believe ASL amps are excellent values--one gets good to very good parts and they're generally well assembled and often are ingeniously designed. I've substantially modified my 805s, and even with all the stuff I've added and changed, they're 100% reliable. I understand that the early Hurricanes were somewhat unreliable but they're much better now.
The amp you're considering may well be excellent, but understand that the 300B tube is one of the most-expensive available new or NOS. I think I'd look for one of the KT88- or EL34-powered triode-switchable integrateds rather than get into 300Bs.