I with you, love the highs, but want them toned down just a touch. My favorite 6SN7 tube right now is the Sylvania VT-231. It pulls the highs down, has good midrange, but has a very thrumming low end. I feel, IMO, it has better bass than the Kenrad VT-231, but the Kenrad VT-231 has very tight bass where as the Sylvania VT-231 has a bit more of a "warbly" bass, if that makes sense.
I'm still a noob tube roller so I don't feel qualified to give you a good idea on tube combos. I think steering clear of RCA for the time being and trying out Sylvania and TungSol would be your best bet.
6SN7 Reference Thread:
^^^^^ Great place to find the pre-amp tube you are looking for. Honestly, I feel the pre-amp tube has a bit more effect on what you are hearing. There is debate on this, but the only time I can really hear the music change is when I am swapping out the 6SN7s.
As for Power Tubes (6AS7)
RCA 6AS7G - Bit Bright and Clean
TungSol or Sylvania 6080 - Can't go wrong, great power tubes.
TungSol 5998 - Pricey, but highly recommended by just about everyone.
Do you have any links for the 6SN7 and the 6AS7 tubes you are referring too?