My system is where I want it be and it sounds awesome...

Have GE Triton One.R. Similar to your GE Reference. You don’t need a sub!
 However —- that Oppo ...
I upgraded to an Oppo 105D with full Modwright mod, including tube power supply and tube dac.  Wow!!!  Difference not subtle. Try it if you can.
Get back on that train.

Btw
if you tube roll, start with the preamp. The Carver amp should be just fine with the original tubes.

The 275 amp comes with either Electro Harmonix or JJ tubes for small signal tubes..  I changed to NOS Telefunken for both the 12au7 and the twin 12at7's.  Big difference.  There are quite a few NOS tubes that will make a big difference in that amp.  Sylvania goldpins, Amperex, etc. are all nice change in the signal tubes.  The output or power tubes are all good to go.  Those KT120's are great, although you can run KT88's, KT150's, or even 6550's.  

Yep I’m not getting up and down anymore tweaking knobs, moving the Reference mm to get the perfect place.  I don’t find myself any longer trying to hear what I can improve on.  Instead I’m enjoying the music without being obsessed of what I can do to make it sound better...Of course that was a lie, but I do find myself enjoying more and tweaking less.  I’ve got about 20 hours on the GE Reference now and they are really opening up...Love them.  But my wife’s gonna crap if she sees the price tag.

I am one of those crazy enthusiasts who keeps multiple systems and extra components in the house. I won’t tell you how many systems because I am afraid someone might impose an intervention! I have sold most of my gear and consolidated down to one or two excellent systems on numerous occasions. Each time I have said that I was “done”. Those reasons included finances, clutter, children, and an irate but very understanding wife … Most recently it has been health issues. Quitting never lasted for very long!