I'm afraid that I can't help with the kinergetics. It could be the room ... some rooms just suck out the bass. It could be that your amplifier is running out of power (passive subs must really suck current from a power amp).
I do know that a REL strata will complement the tc-50s very well, and may well give you what you're looking for overall. Musicality with a bit of grunt. However it will probably set you back a bit. Mine cost $800 used. No it's not for sale ! :-)
Something of a compromise between the spica imaging and having a bit more bass might be a used pair of Epos es-14s, though these are rear ported and will have to be a couple of feet from the rear walls. They're nice speakers and are about $500 or less used. Other possibilities are Mission 753s. If you really want bass then I liked B&W DM603s ... real rockers, but not for classical.
I do know that a REL strata will complement the tc-50s very well, and may well give you what you're looking for overall. Musicality with a bit of grunt. However it will probably set you back a bit. Mine cost $800 used. No it's not for sale ! :-)
Something of a compromise between the spica imaging and having a bit more bass might be a used pair of Epos es-14s, though these are rear ported and will have to be a couple of feet from the rear walls. They're nice speakers and are about $500 or less used. Other possibilities are Mission 753s. If you really want bass then I liked B&W DM603s ... real rockers, but not for classical.