I agree with atmosphere's comments, but your A 21 would pair well with a Parasound JC 2 preamp. The used market seems to be around $2K. The JC 2 has been characterized as approaching an ideal strait wire with amplification.
If you want to integrate it into an HT setup, Parasound can add a BP capability so any channel can be unity gain. The cost of the mod is reasonable.
Disclosure: I use a JC 2 BP with a pair of JC 1 monoblocks.
db
If you want to integrate it into an HT setup, Parasound can add a BP capability so any channel can be unity gain. The cost of the mod is reasonable.
Disclosure: I use a JC 2 BP with a pair of JC 1 monoblocks.
db