Thanks guys!
I have two amps that runs these types of tubes: a Music Reference RM-9 (mk. 1), 100 watts/ch, fixed bias, and a Quicksilver GLA, 40 watts/ch cathode bias. The RM-9 has lots of bass slam/attack while still having a lucious midrange - great all around amp for any type of music! The GLA has much less bass slam/attack but is far more delicate sounding - truly excels at chamber music and small scale acoustic but doesn't do rock music extremely well.
I'm sure the circuit is extremely important in extracting those flavors. I'm just looking for gross, even gratuitous, generalities. All I've ever heard along these lines relates to the EL34 (lusher midrange) and KT88 (tighter bass). I'm wondering where the other types fall in this blood line. It's too expensive for me just to buy a few quartets to try (8 power tubes in the MR, 4 in the Quicksilver, both requiring matched quartets). Any help is appreciated!
Oooooops! I forgot to include the TRUE 6CA7 and the KT90!