How does it colour the sound, if no Cab Sim is enabled on the OxBox?
EDIT: Oh I see, is it an issue with the Ox passthrough itself?
There is a DI option at the Simulation side, but I would put the DI box before the OX.
The OX is cool, I'm not head over heels on the cab simulations, I still feel it is aimed at lower gain applications even with the V30 cabs.
The magic is the room simulation, it just makes the whole experience a 100% better. Really hard to get close to it, I can only approximate it with using the UAD Ocean Way Studios plugin or mixing in room IRs with Libra with a whole bunch of EQ. It's really tricky.