The AU-217 Mk II is 40wpc, the original Mk I (although it doesn't bear that designation) is 30wpc and a fine sound it makes. Landed mine off Ebay, in near mint nick, fully serviced and delivered for £33 late last year and it's the easiest amp to listen to. My AU-717 is currently in for servicing, so that will have had some special TLC, but the 217 easily drives the Mission 752s (which are 89db sensitivity) to comfortably loud volume levels. No signs of strain unless it's really pushed.
The 717 has no such issues. I've turned that up briefly and the speakers don't come close to distorting. Wonderful amp, superlative build. THD is 0.0025%, which isn't bad, but nothing like the current likes of Cambridge's 840A (0.001%). Then again, there's a 33 year old amp doing the business in my system and it's doing it well. I got mine for £200, so that one has gone for £350 just shows how this brand might be coming on to more people's radars now. It's 85wpc by the bye and dual mono internal construction. Two huge power supplies and 4 x 15000 microvolt capacitors on show. Beefy!!
For your budget, the 217 is the minimum starting point for the n17 series range I think. There was the 117, but that's apparently no great shakes. The 717 has a newer model in the 919, released around 1979.
Sound-wise, expect good control, the kind of sound you can listen to for hours, plenty of power (they were conservatively rated IMO, a la NAD) and fine build. The 717 is handbuilt pretty much throughout. You just don't get that level of input nowadays (but technology does being other benefits over time of course).
I'm delighted with both of my amps, can't recommend the brand enough, except to say "caveat emptor" and watch out for the gear from the early 1980s onwards when quality slipped. Otherwise, you could do very well.