Picked up a A-25 Dual Servo Amp for $24 locally - currently hooked up to some Realistic Nova-5's - $14 in the kitchen. I need a tuner though. I'm waiting for the right one........it could be a while.
I had an A-25, 40 w/ch, and it is a very healthy 40 w/ch, too.
This amp was one of Onkyo's "slimline" models, silver face, and a very clean, attractive amp. Even today, it would mix and match with some of the Onkyo silver face units and not look out of place.
The A-15 was similar. The A-25 used STK1050 hybrid chips for output, one for each channel. The A-15 used a single STK463 (I think) stereo output chip, which drove both channels. The A-25 had speaker output switching for Off (when listening to headphones), A, B, or A+B (in series). The A-15 had just Off, A, A+B.
Also, the A-15's phono stage was for MM cartridges. The A-25 had a pushbutton under the door, and indicator lights, for MM or MC cartridges.
The Onkyo T-15 (analog), T-25 (digital), and T-35 (digital) are great matches visually, and perform well.
The T-15 has a ferrite rod AM antenna on a ball joint on back, which I think can be disconnected. It just does not perform. This tuner very much needs a separate loop AM antenna. FM works great, and the servo lock feature really locks on a station.
I saw a T-15 on ebay just recently, and also T-25 and T-35 tuners.
If you will IM your email address, I can send you a pdf of an Onkyo brochure for the A-15/T-15 combo, and T-15 owner's manual.