INPUT/OUTPUT IMPEDANCE

I have no knowledge as to how the Anthem and Parasound amps compare sonically.  But as I and George indicated earlier impedance compatibility is not an issue in this case.

Regards,
-- Al

Either is likely fine from an input impedance perspective. 

Usually it is tube pre-amps that have higher output impedance that some SS amps can handle better than others typically with input impedance ~ 40 to 60 Kohm or higher. 

Anthem amps are products I have heard recently that I would consider owning. Have not heard Parasound but those are also highly regarded in general. Either should work well and sound good it seems in your case.

If you think you would ever consider using a tube preamp with the amp you choose I would choose the amp with the higher input impedance which sounds like the Parasound, all other things being equal.

As George alluded to that is most likely to be an issue in the case of tube-based components, many of which use a coupling capacitor at their outputs. The impedance presented by a capacitor increases as frequency decreases, so the output impedance in the deep bass region can be much higher than the specified output impedance, which is usually based on a mid-range frequency such as 1 kHz.

In the old days tubes got around this problem (in balanced systems) by using an output transformer. This enabled the output to also not reference ground, something that is *very* tricky to do without a transformer! We developed a circuit that allows for direct-coupling of the output in the balanced domain but otherwise acts much the same way as an output transformer does, although wider bandwidth and less distortion. So there are tube preamps that can drive loads like this with flat frequency response; in fact can drive loads as low as 600 ohms.

Ok but practically to keep tube preamp options open it’s much safer to go with an amp explicitly designed to handle that which spec wise means higher input impedance than 10kohm more like 60-100kohm typically with most products I have seen.
Bel Canto ref amps are a good example. Older models with stock Icepower modules only had 10k input impedance and users with tube preamps reported poor results. Newer models since cost more but added custom input section with 100kohm unbalanced input impedance. Those like the ref1000m amps I use with ARC tube pre-amp are a match made in heaven.