BEST TUBES FOR AUDIO RESEARCH PRE-AMP (LS-16)

Just looking for input on people's experiences with pre-amp tubes for my Audio Research LS-16.

For the last couple of replacements I have chosen GOLD LION E88CC/6922's.

Before those it was Electro-Harmonix 6922's.

I think the Gold Lions are smoother  (less bright)....which is to my liking...and still detailed...nice midrange...

I mostly listen to vinyl...system is Audio Research LS 16 pre-amp...Audio Reserch 100.2 power amp  (solid state) VPi Scoutmaster TT,,,Wilson Sophia speakers  (first series).

Also any thoughts on how much of an upgrade an LS-26 or LS-27 would be.

Thanks!

Greg