For the Traynor, I'd dump the Sovtek EL34's. They are too
thin and get microphonic in a bass amp way quick. They also
can't take much voltage and have a lower volume. I love fat
bottle 6CA7's for bass. (Unfortunately, the hifi crowd just
'rediscovered' them and their prices are through the roof
compared to even six months ago and the only factory(EI) that
still made them is out of commission.) I like the EI's better than
old GE 6CA7's, too. The EI's have a rougher texture which
gives better definition to bass. GE's get a little too warm and
turn muddy. Old Sovtek 6CA7's fit nicely between EI and GE
in terms of tone and will last too, but they haven't made them
for awhile. I tried Svetlana EL34's and they were OK but
lacked bottom and turned microphonic.

My preamp tubes are Telefunken. They're the absolute best in
terms of warm tone and resistance to microphonics. I found
GE's too thin and midrangey, RCA's(gray and black plate)just
sounded sort of lifeless, and I liked Sylvania, but they get too
microphonic and weren't as warm as the Teles. Although, I still
use a JAN Sylvania 7025 as a driver. It gives the tone just a
little more drive(no pun intended) than the Tele, but for
preamp, the Telefunkens were the best. Sovteks sounded
downright awful with the only things worse being Chinese. I
have some JAN Philips 12AX7WA's and GE 12AX7WA's
but I have not tried them in the Traynor. (Although that Trace
Elliot VR400 has the Philips and they sound much better than
the Siemens that came in it.) 

Also for bass, I can't stress the importance of a SERIOUSLY
heavy speaker cable enough. Tubes don't damp as well as
solid state and need the best connection to the speaker
possible. My cables are 10 gauge solid core wire. Solid works
better than stranded for bass because it lets more low
frequency stuff through compared to a stranded wire. It's the
other side of that skin effect coin. Longer wavelengths need
more core mass. Don't waste your money on those boutique
$100 cables, though. Just head up to the hardware store and
buy the wire in the heaviest gauge you can get two conductor
in (10 awg is the biggest that will fit in a 1/4" plug though. Go
bigger for posts)and make sure you use oversized 1/4" plugs.

Psycho Bass Guy, Many thanks for answering my question
before I posted it! I was wondering what your feelings were
about 6CA7 vs EL34. From your post I assume your Traynor is
a Custom Special. A few years ago I bought a Custom Special
for $75, and have been intimidated by it ever since I opened it
up for a look! Marshall 100 watters don't phase me, but the
Custom Special makes me feel like I'm just a guitar player.

My Traynor is a regular YB-1A, but Traynors are pretty similar
to each other. The 6CA7 was one the secrets to the old
'Marshall Sound' and EVH's brown tone back in the early 80's.
When GE stopped making them, a lot of people just plugged in
EL34's and didn't stop to think that the sound would be
different. The bass response of a 6CA7 isn't actually that much
more than a regular EL34, but the 6CA7 has more headroom
and doesn't lose it to breakup. 6550's stay cleaner longer, but
don't have the same midrange snarl that goes with the 6CA7's.