Yes, I hadn't thought of the centre channel application, perhaps thief was a bit harsh! But I was literally just about to press the "buy" button before I thought to ask the forum so I'm doubly indebted, firstly on the suitability aspect and secondly on the "single unit" catch.
In my excitement to learn all I could about the A30 - I did what I criticize others for doing constantly, I perused YouTube and found a review by "Z" where he seems to be driving a huge pair of floor standing speakers with an A30. I'm sure if I researched the specs on those speakers they would turn out to be super efficient compared to the Polks.
Anyway, I currently have a Yamaha R-S201BL powering a set of Bose 201 v2 straight from the back of a desktop with no DAC and an Elac debut S8. The speakers were inherited along with an Onkyo amp of about the same vintage and were a huge step up from the tiny powered desktop speakers I had been using. When the Onkyo failed I replaced it with the Yammy which sits on the floor because of a lack of desk space. Unfortunately it competes with a cattle dog for that space, specifically, the cattle dog has been using the volume control as a pillow and now I have a very audible buzz at all volumes and a hellacious noise whenever I adjust the level.
My wife was happy for me to replace the Yamaha as long as I got something small enough to sit on the desk, and BT enabled to allow her to use it easily as a secondary user, myself being the resident "DJ" would be hooked up via USB. The A30 leapt out as a complete solution but during the wait for it to be restocked I scratched below the surface and decided to get a Topping E30 for better DAC values. And then, of course, I recalled my own days as a "budget Hi-Fi enthusiast" where it was drummed into me that the speakers were the most important part of the system and one should spend the same again on them as one had spent on the rest of the kit, combined.
So I've gone around in a big circle, now looking at a pair of Klipsch RP 600M 96db sensitivity (Thank you franspambot!) and also thinking I should really look at alternatives to the A30, which is funny considering I was "building out" from that as a starting point in the first place
Thanks very much for your responses, like most I spent months as a guest just reading everything I could and I can't express how valuable this forum is to folk wanting to learn.