Honestly, my first thought was if you've only spent an hour chasing tube info & opinions on the web, you've barely dipped your toe in the water.
Most of my tube-amp-tweaking was in the pre-internet days, but I found the Tube Amp Book by Aspen Pittman (founder of Groove Tubes) very helpful. Note that currently a GoogleBooks search actually previews some of the pages (116-134) comparing different preamp & poweramp tubes.
The Groove Tubes website has some comparisons. There's also guitaramplifierblueprinting.com which seems to be kind of an offshoot of the GT website.
Also vacuumtubes.com has comparisons.
Way back when (the 90's) Guitar Player magazine ran quite a few articles & columns about tube comparisons & swapping & amp tweaking. I don't know if any of those can be found on the web, but it's worth a look.
My own personal experience (again, roughly 15 years in the past) is that the interaction of tubes & amps & guitars & the player's ears tends to be . . . . highly individual.
Maybe it's just the specific tubes in your amp, and you could replace them with new EH tubes and be happy, maybe EH tubes in general are too bright and you would be happier with a different brand. Some brands even separate tubes by country of manufacture, giving you even more options. Maybe (as Bob suggests) you could try a variation on the 12ax7.
My point being that while experimenting with tubes can be great fun, don't be too disappointed if your real-world experience doesn't match up with the info you find. Lots of people will swear by NOS tubes, but you might hate that particular
set of Ampegs in your
amp with your
And like Bob points out, power tubes and speakers also play a big role in the sound of an amp.
P.S.: I'm 99% sure any 12**7 tube can technically work as a plug-n-play replacement, but in practice, the 12au7 and 12ay7 are too low-gain - you could try a 12at7.