Is upgrading pre worth it?

I agree with the suggestion of a passive preamp.  I got a Creek OBH-22 Passive Preamp, primarily to use as a remote volume control.  But, it turned out to be quite a good preamp - incredibly transparent, clean, clear, detailed, dynamic, etc.  It just passes the signal on to the amp and speakers without any distortion.  

Hard to believe - but it seems to sound as good as my 40 times more expensive ARC Ref 5se active preamp in many respects - though, the ARC may have a bit better soundstage... not sure... it's so close.  

Of course most passive preamps are very simple (e.g. unbalanced interconnects, few sources, etc.), but the quality of the sound can be amazingly clean and clear.  

But... if you want the rich, warm, sound of a tube preamp (really distortion), then you won't find that in most passive preamps.

Fortunately, the Creek OBH-22 seems to match most of my equipment pretty well - so, it is a bargain for me - though, I’ve not tried it with all of my various speakers, amps and sources.

Not an EE but, I agree - Impedence, gain and current matching is a critical factor in attaining the best sound from your components. I became aware of impedence and gain matching, with some headphone amps I have / had.

I wondered why the X-CAN v3 would sound great with my high impedence phones and less so, with my low impedence phones, while the X-CAN v8 just the opposite. It turned out to be an impedence matching issue. Makes all the difference.