Tube Pre-amp Suggestions.

I switch between a Pass XA-25 and a Dennis Had Inspire "Firebottle" HO (high output) SEP...speakers are modded Klipsch Heresy IIIs (prefer the titanium mids in the IIIs to the poly re-designed mids in the IVs).

There are a few Audible Illusions models on the used market.  I have not heard them but consistent praise ... service, on the other hand consistent difficulty:

https://hifizero.com/index.php?q=audible+illusions

https://www.audibleillusions.com/

@kds https://forum.audiogon.com/posts/2808600

The Rogue RP-7 Preamplifier features two pairs of balanced XLR inputs. It also includes three pairs of RCA line level inputs. 

Another vote for Audio Research.  I have a SP9-MK2 and have been itching to get something newer and still haven’t pulled the trigger. Depending on you finances, the LS-28 is really good and of course there’s the REF series.

Oh and why are you wanting to sell 8 watts of Class A goodness?

The benefit to a reasonable tube preamp there are always better NOS tubes that will make it better or tune to your listening preference. 
I use Brent Jessee Recordings and Supplies on line. Super informative and probably knows my equipment better than I do