Help wanted spending money and improving my system.

I’ve got the upgrade itch and would like feedback on what piece should be replaced or what should be added.  If this system was yours, which piece would you replace and what would you buy as a replacement or what would you add to improve the sound/experience.  I’m not considering replacing my cabling at this point in time.  Please, 1 item only.  So, what would you add or replace?  I’m very happy with what I’ve put together, but I’ve got the itch, and scratching is not enough!!  Current system:  Carver Crimson amp, Primaluna Dialogue preamp, Schiit Yggdrasil D/A, Schiit Lokius equalizer, Jays CD player Mk III, Oppo 103 (for SACD only) Thorens TD145 with Ortofon 2M Bronze, M&K V75 sub, Klipsch R-15 sub, Roon Nucleus, Mac mini server (for iTunes) and Goldenear Triton References, home made bass traps.

How about RCA cables. Check out Hapa Audio cables, specifically the Quiescence series. Even in my budget setup they made a world of difference in resolution and soundstage.
Listen to MC and/or treat your room. Your system components are fine as is and as someone else has said, if you make an upgrade to one of them, where do you stop?
If vinyl is important to you, think about an upgrade to your turntable//cartridge/phono pre rig. 
Since Synergistic Research's High-Frequency Transducers have been mentioned, anyone care to share their experiences?

There seems to be a decent explanation here: SYNERGISTIC RESEARCH HFT X.

What if you've got a Home Theatre System with too many speakers to treat?