I have the Orch Reference also, and thought the same as you, to possibly disconnect the pre stage and add a better preamp, line in. But as the above poster correctly advises, no.
The Jadis dealer in Colorado , Frank, sent me a pr of Cabasse MTM's, can't recall the name, I thought the bass was abit thin, etc. Just not enough, sent them back same day, ($100/return ship!)BTW, Cabasse is no longer in business. I just bought the Seas Thor speakers at 4ohms, 86 db. The Orch Refer just does not offer the dynamics in the highs that i LOVE, the mids are quite real, but still the musical image is slightly supressed, a cover over it. Bass is not too bad. But I'm going further. I just got 2 old Marantz's off Ebay, and hope I get some dynamics to make these MTM Thors shine. As in all things audio, there is a trade off. I have a feeling the Jadis is going to market. Will post everyone on results. I wanted a used Electrocompaniet 70 watt, but too expensive. If the Marantz does not work out, I'm going Cayin 6550 mono blocks + the Ming Da pre, a $3K investment. Will keep everyone posted.
The Jadis should be perfect for Cabasse, because those are very high efficency speakers. But not my cup of tea. The Thor's are. BTW I plan to add a W26 woofer to the Thors, biamp. The Cayin cdp has 2 outs, one tube to one Marantz to the Thors, the ss out to another Marantz + the Cerwin Vega xover to the Seas W26. ???? The Thors need that extra bass.