What made you decide on the A21?
What do you consider affordable? For power conditioning
this PureAv unit is pretty nice, I bought two and they are great for $55. I like PS Audios units alot, but a Quientet will be closer to 10x the price of the PureAv.
As for cables I will throw down my usual recommendation of Belden 89259. Great cable, well shielded, and teflon dielectric. If you want to go cheaper perhaps 1505 is more up your alley, you can get it at BJC for $35/pr.
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Bedroom Rig: Red Wine Audio Analog Modded SB3 -> Promitheus Ref3 TVC -> EVS 500M -> Gallo Ref 3.1+SVS PB2+
HT: Pio Elite DV-47ai -> B&K Ref 50 -> Rawsonte 200ASC IcePower Amp-> Mirage OMD-5 x 2 - GIK Acoustic Treatments - Buttkicker LFE
PC Rig DIY Paradise USB Monica -> Promitheus Ref1 TVC -> Monarchy SM70 -> SIA Rothschidle A2
Workout Rig DOS SB3 -> Endler Attenuators -> Rawsonte LM3886 Gainclone -> LSI9