Tube gear, such as the Bottlehead Moreplay, tends to have a relatively high output impedance; Moreplay has up to 3.2kOhm, according to Bottlehead. They don't publish schematics, but from what I understand, each channel has a triode connected 6П6С (~6V6GT, plate resistance 2.4kOhm) with bypassed cathoide bias resistor and a 5kOhm anode load, followed by a 10k pot and the output. My calculations give 2.9kOhm, rather than 3.2, in the worst case, but I don't know all the details.
Omicron, on the other hand, has a lowish input impedance of 6 kOhm and, if you use crossfeed, the input impedance gets a tad lower above 1kHz. While this has not been a problem with solid state sources, with a tubed source like Moreplay it might be. Specifically, you may obeserve (1) a lower output level when Omicron is connected; (2) "bass boost" when using crossfeed; and (3) higher distortion if the 6V6s get overloaded ny Omicron's input impedance (the datasheet says 3.5kOhm load, which is about 5kOhm || 10kOhm, that is, the load impedance is expected to be high). All these effects would be dependent on the position of the output pot (the one closest to the power switch, if my understnding is correct).
So try it by all means, but don't be surprised is this particular match is not made in heaven.