Where do I go from here?

• Marantz AV-7005, pre/pro (with balanced outputs and 1.4a HDMI);  Rotel RMB-1565, surrounds and center;  Rotel RKB-650, mains w/ bi-amping;  Martin Logan Motion 20, mains;  Martin Logan Motion 8 Center; Klipsch SW-10, sub;  KEF iQ-5, surrounds;  Klipsch RS-41 II, surround backs
  

Alright y'all, here is your chance to help out the newbie with your thoughts and opinions. Thanks in advance for what you may offer.  I have the above system, which is sounding really nice, with many of the qualities I've been looking for, but the upgraditis is creeping in, (again, sigh) and I am wondering which of the components may represent the weak link to my music listening nirvana?  As some my recognize, I recently added the Motion 20's to the lineup, much to my satisfaction, but where might I go from here.  I'm thinking my better half may let me get away with another $1500-2000 before I'm sleeping with the system and not her, LOL.  Since I'm more interested in the musicality of the system, listening to a mix of female vocal, rock, and dipping into the ambient realm now and then, I'm considering the replacement of the Rotel RKD-650 with something in a nice stereo configuration, possibly 3-channel to pick up the center. I'm really looking to broaden and deepen the soundstage as much as anything.  What do you think?