Update: getting a lot of great use out of the ISP SP at home and can recommend it as a super light and powerful class A/B power amp, bizarre power supply be damned.
Using it bridged/180W with the volume around 1pm with my Recto 2x12 and setting the overall volume with my FM9.
I'm thinking of trying it at a gig next week, we'll see. Sounds really good with the Cornford 50 model. By far the happiest I've been with any of the models.
(Also, Katana 100 head is now sold.)