Buying used: Parasound A21 or A21+ ?

I've decided to get a Parasound Halo amplifier, but with limited budget, i can't afford new, so it's either a used A23 or A23+. I like that the A23+ has a bit more power, but I wonder if the apparently subtle upgrades are worth paying a premium.

Thanks for advise on other amps, but I'm set on a Parasound Halo, to go with my P6 preamp. I like their sound signature, I guess.