Tube Upgrades for Cayin A-50T ?

I'm looking to upgrade the tubes on my A-50T. The tube compliment is:

Mullard push/pull EL-34 (4), 12AX7EH (2), 12AU7EH (2).

I'd like to get a bit more bass, fullness and warmth out of the amp if possible.
For fullness and warmth, you might consider the mullard 12ax7's (nos), it's possible that the newer "Groove Tubes" will fill the bill, as I have not heard them as yet, but their price makes them an attractive option. I have not been impressed with base response or warmth from my Mazda 12au7's, so I would not recommend those to you. Perhaps others can lend some advise regarding the output tubes and the 12au7's.
Thanks. That's the kind of info I'm looking for.
Anyone have recommendations for the EL-34s?
Just in case anyone else is interested, Vacuum Tube Valley recommends the following for the Cayin A-50T tube upgrade:

JJ Kt77 (matched quad)
RCA 12AU7 nos
GE 12AX7 nos