[morzh]

Tomie

The DC resistance is not that important.

What is important, first of, is the input/output impedance ratio.

If you use the 125E CT transformer, make sure you connect the outputs that will match your impedances accurately.

Then, to a point, the primary inductance (or rather parasitic primary inductance) also matters.
Also the core material.

125 series has 150Hz-15kHz band that means that it should work fine for your purposes, should the match be good.

So, find out the speaker impedance, find out the primary impedance, and use the chart in the datasheet to see what connection provides for the closest match.

You want 10K P-P impedance. If your speaker is 3.2 to 4 ohm, you need 2-4 outputs to get you from 9K to 11K impedance.
For 3.2 Ohm, if it is the case, also try 1-3 outputs.

Last, if you could find a transformer with better low end characteristics, try that. Maybe this is what you are having, and the Zenith xfmr simply has better low end number.