SI monoblock/bi-amping questions

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preamble:
I've been using two SI 5066's, one for the woofers left and right, one on the mids&tweeters l&r, with very nice results. Not true biamping, I know, I know.... And besides, running the amps as monoblocks seemed to be a waste of those two unused output channels.

The SI input sections are bypassed, with 3.3uF polypropylene and 20k metal film series resistors jumpered in upstream of the onboard surface mount input caps, 50k resistors from signal to ground at the input rca's.

I've modified my tube preamp to have dual outputs, running the output coupling cap of each side to the junction of two 4.7k resistors to provide some channel isolation. It seems like I lose a little immediacy, a little air or vibrancy or {insert audiospeak here}, so I'd like to remove those resistors from the signal path and go back to single L/R outputs and one set of interconnects.

body:
Last night I changed one of the SI's to mono input, connected one end of two 10k resistors to the input RCA, other ends to the input caps. Now that amp's "left" output powers the mids/tweeter of the left speaker, "right" output powers the left speaker woofer. (Bi-wired, no common grounds).

Can I do away with the 10k resistors without halving the input impedance by running the channels in parallel? How do I compute the input impedance with the 10k's in series before the input cap and 20k gain setting series resistor, and a 50k to gnd at the rca?

I've managed to confuse myself, and I feel I'm in a "borrowing from Peter to pay Paul" situation.

Any ideas much appreciated!

John
 
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