I'm in agreement with the others, as I find it hard to believe the Pass amp is the problem. This review on the Pass Labs X250.5 describes the high frequencies as natural, which has been my experience with other Pass products.
This may be the review for your T+A Criterion TCD 110 S that Tom is referring to. The part about being "shouty" is toward the end, but prior to the "Conclusion" section.
IMHO, the issues you describe are not related to each other, so making a single change will not solve both problems. As Peterayer suggests, speaker/room interaction may be a problem.
If you don't use the subs, do you still have the mid-bass bloat? Also, curious as to the cables you are using, digital, IC's, and SC's.