In quest to find a lightweight, public transport-friendly amp for rehearsals and small gigs, I took a chance on sourcing one of these from the US.
Spec as below (with measurements obviously put into metric):
12.7 x 17.8cm
500 watts @ 4 ohms, 300 watts @ 8 ohms.
THD less than .1%.
Full array of protections built in against shorted output, over temperature, DC fault (for speaker protection), over/under supply voltage etc.
Tonally transparent with no unwanted coloration.
Not sure how much depth one can go into for such things, not being a power amp aficionado, but this really does do what you need it do. Very quiet (aside from some fan noise discernible up close) and bloody loud. The fact that it's tiny and light is a big bonus too. Photos above my amp give an idea of scale; If my hefty valve amp had feelings, it'd be a wee bit anxious about its place in the pecking order right now....
I bought this after enquiring on Jay's Facebook page; even after postage and customs this came in at around £265. There may be other similar products for less money but lower power (TC Electronics) or bigger, more powerful items (GSS Baby Sumo) but this really does do the job for something you can have in a studio or slipped into your gig bag.
Please do send a message if you'd like to know more.