The new production Tung Sol 6V6 is an excellent sounding tube. RFT rectifiers are good and not expensive. Choice of an input tube depends on the rest of your system.

I've found in the M-T, using 6V6 exclusively, that the key is finding synergies among the driver (input) tubes and the output tubes, for a given listening room condition (mainly the speakers' interaction with these conditions and the sourcing's profile characteristics.)  

The rest of the tube choices can enhance or detract from this synergy, but at a lesser effect.  The exception of course, is the low-frequency profile impact that the OA3 ... OD3 series can bring to 'color' that synergy. These would make it lighter or darker (detailed or warmer), but won't interfere with the essential job the drivers and output tubes have worked out together.

Whether this structure will remain across other non-6V6 output tube alternatives is something I ignore, but suspect the same outcome.

An additional variable, essential in my case, but maybe immaterial when using large floor standing speakers, is the application of a Sub-Woofer.  You can get away with OC3/OD3 output voltage regulation (i.e., lighter, more detail-retrieving with much less low frequency profiles but tighter low-mid range bass), if you adjust your well-placed Sub at a cross-over in the 65-55 Hz range.  

All that missing depth can be more than compensated setting the Sub's volume accordingly, especially when the Sub is being fed by the M-T's Pre-Outs, as these impart the M-T's signature at line level.

Yesterday I paired the stock JJ 6V6 with Psvane 12AT7's and was shocked at how good the combo sounded. The soundstage was wider and deeper. The amp seemed more powerful. Sonics were harmonically rich, detail and texture...excellent. Synergy. When these JJ die I'll get a pair of the cryoed and tested ones on fleabay. As always...YMMV.