Schiit Freya+ vs. high end (e.g., Mcintosh) ?

Having burned in the stock JJs on my Freya+, I have ordered quad Tung-Sols with all options: balanced triodes, low microphonics, high gain, matched. My first rolling experiment on this pre with 6SN7s. Bass on JJs can be tubby (some listeners like this sound; on most material I want more definition) and female vocals can lack clarity.

@shkong, if I go next to a pair of NOS RCAs, should they go in buffer stage rather than gain stage? (This assumes Tung-Sol or JJ in gain stage).

Same question for @wolf_garcia; if I get only a pair of NOS GEs to begin, try them in buffer stage?

Wolf, shkong, thanks for the detailed info, which will certainly inform my rolling experiments. All systems & ears differ, but there are areas of wide consensus so there is a great value in sharing experience in a forum like this. Apologies to OP for the interjection. Didn't want to start yet another new string on this popular product.