Linn system: speaker matching

My system consists of: Linn Karik CD Transport / Numerik DA Converter Linn Majik (used as preamp only) Linn LK85 amplifier Cardas Lighting Digital BNC interconnect and Sync between Karik and Numerik Linn standard interconnects elsewhere (the ones that come with components) Linn K400 bi-wire speaker cable I recently acquired a pair of Silverline SR17 monitors. They are wonderful, but the music does get a bit "thick" in the lower midrange. I suspect that what is happening is that these speakers are revealing a characteristic of the system that my last speakers (Sonus Faber Grand Piano) didn't. The speakers otherwise have an astounding soundstage, and they make music with great detail and authority. When listening, one gets the sense that these lower mid-ranges are "tight", or that they are being somehow held back, or restrained. The sound there somehow has more density or weight than it should. I'm tempted to describe it as sounding "congested", but that isn't quite right. The reason that word comes to mind is that the feeling reminds me slightly of the sense of "pressure" on the ear that one experiences after a fast change in altitude (e.g. a fast elevator in a high-rise building). The adjectives that keep coming to mind are "weight", "heavy", "restrained". It seems like these ranges want to break free, to get more "air" and "speed". Again, all of this applies to the lower midrange. It could be anything, but I'm wondering if it might be a cable issue. Like I said, I sense that the problem is that these speakers are revealing a limitation in the system; the performance of the speakers is otherwise so refined and strong. Any suggestions for what I might try? Obviously, I’d like to try changes starting with the least costly – as I mention in my comments, based on what I’ve heard before I suspect that it could be a cable issue, so maybe I could start there. TIAb