Hi OP,
Unfortunately I don't see an easy way for you to accomplish this. Your integrated has preamp outs, so you can connect your sub's line level (RCA) inputs this way but there's no way to limit the amount of bass that reaches your speakers. However, you can plug the ports, which I often recommend for 2-way speakers with subs. This will somewhat reduce the excursion below the tuning frequency but reduce the output so you can turn the sub up higher. this will make it easier to integrate the two.
If possible however an approach that did let you put a high pass filter in line with your main amplifier would improve upon that. Maybe talk to MW and see if they have a suggestion?