Help selecting a new preamp

Well, to simplify the SYS just might do the trick. To improve sound it depends on what improvements are called for. 

I own a SYS, and it is truly simple, having only 2 inputs and single output with volume control.  As a passive the sonics of your system will be determined mostly by the other components. Not costly to try.

I also have a tube preamp in my main system, I enjoy the impact tubes bring to the sonics, more 'bloom and air'. There are many to choose from that retail for far under your 5K budget and would fit nicely with your other components. If wanting a tube pre, check out Brown Audio Labs, Quicksilver, Don Sachs, Jolida, and the aforementioned Schiit Freya to mention a few. 

+2 for the Schiit Freya

Don Sachs Model 2 preamp or one of the new generation of Suprateks would be excellent and leave you some money for other upgrades. A good preamp will make a significant difference in your system, at least in my experience. I have owned two Suprateks and currently own the Sachs preamp, and can attest that either would be a great choice.

Waltersalas-
I am interested in hearing your thoughts about how the Sachs compares to the Suprateks you owned. Would you be willing to share some thoughts on that?

Wyred 4 Sound STP-SE stage 2 is an great sounding solid state preamp.
https://wyred4sound.com/products/pre-amps/stp-se