Neutral-ish Speaker Cable

@roadcykler Everything matters and cables and interconnects can matter significantly depending upon design and brand.  
@jaybe I recommend you add WyWires Platinum to your list in your price range.  Moving to WyWires after auditioning a number of brands in their price range made a significant improvement in achieving natural timbre, staging, imaging, dynamic and balance.  Balance was the key.  Nothing exaggerated at any point in the frequency spectrum with vivid detail across the spectrum.  Read professional reviews which confirms my opinion.  Contact Alex Sventitsky, designer and President.  He is a sincere and down to earth person … always helpful.  They are currently running a 35% off sale on the Platinum series.  
https://wywires.com

Audition and see if your ears confirm my opinion and the pro reviews.  Good luck.  

PS  No vested interest. Just a very satisfied customer.  

I would let the new preamp run in and then roll a few tubes before changing anything else (assuming that you are using the Rogue RP-7 recently posted about).

A couple pairs of Amperex 12au7 short plates will cost $300-$400 and long plates around $600, or so.

I would not tube roll until you have @ least 200 hours on the preamp.

DeKay

@dekay Thanks for remembering that. Yes the Rogue has been running non-stop with 200+ hours already and I have a set of burned-in $$$ Amperex Holland 7316s installed. Heavenly.

@jsalerno277 Not familiar with the WyWires, thanks for the heads up.

@sls883 The Fideliums are so cheap and so highly rated (cable of the DECADE) that I just ordered a pair. And returnable. But still looking and still taking feedback.

And thanks for all the other great input from everyone.