The three Stereomour inputs go to a dual 100K pot, same as the SEX amp. This impedance is too high to drive an auxiliary pre output. The pot goes directly to a single 12AT7 which is the stereo driver tube.
Yes, the new output transformer and plate choke are of similar quality and design to the Paramount iron; there is a slight compromise because the same iron (with a tap on the plate choke) will be used for a revised SEX amp as well. This compromise will result in an estimated 35kHz high frequency rolloff for the Paramour (it's higher for the SEX amp) but somewhat better deep bass performance. I'll know more when we've put the final revision of this iron into the last (I hope!) developmental prototype of the Stereomour, sometime in the next few weeks.
Mike at Magnequest has said he will produce a compatible output transformer with a 4K impedance. Currently we are using the same upgrade transformer for Paramount and Paramour; this is an excellent transformer (derived from the TFA-2004Jr with some technical improvements for Bottlehead), it's kind of overkill for the Paramour. The new transformer will be smaller than that, more well-matched to the 2A3, and a bit less expensive. The plate choke will be identical to the current Paramour plate choke, except there may be an option to use a different version of the choke if the Stereomour is intended for the 45 tube.
Hope that clarifies teh situation a little!