TVC with subwoof or cdp direct to amp & sub

I am intereseted in using a transformer based volume control or a CDP that allow direct connection to amp. Are there any problems with the addition of a velodyne DD12 sub.

My amp has 100K Ohms input impedance. I can't find input impedance of the amp of velodyne sub.

When using a line level input, would CDP or TVC provide insufficent voltage to the amp if sub-amp is shunting current from the amp?

I think i can circumvent this by using speaker level input but line level connection seems to make more sense. (Using sub with speaker level input may require more internal processing.)

I'm using an Audio Zone PRE-T1 TVC which has two sets of outputs. Highly recommended. BTW, how is the ASL 1009 working out for you?