Haven't you ever tried your tube preamps with different poweramps? The mix/match is part of the fun, I use to hook two amp heads in tandem with their opposing power amps hooked up just to hear new sounds. Also, I went from 8 sounds to what 105 right now and growing, my amp gas is cured, when I get tired of a sound I just dial in a new one, always fresh and I've used some amp sims I never would have tried as real amps,ear opening.
Of course I have tried different combos - but as I said, I like most, tend to dial in the same basic tone on whatever I am using. I in no way get needing 105 different tones at a gig.And I simply did not find the Axe sims of preamps to match my tube preamps tonally anyway. Maybe it does now, I don't know. And for the price point I can get just about any tube pre I would like.
For me the preamps entirely change the character of any sound I dial up enough for my uses. I've actually consider buying all the tube power amps available and making a midi switching matrix to use them all, then again I'm really happy with one six space rack, don't really want to haul a ton of gear again. Lately in the interest of poweramp options I'm thinking of two stereo power amps with different tubes in each channel, and some creative switching. El34, 6l6, kt90,kt120.
Then again, I see no point of hauling multiple power amps to a gig with an Axe. One of the main advantages is the downsizing. Might as well still take multiple heads at the point you're hauling multiple power amps. With racks, the power amps would be heavier than most heads, and take up more room.
I'm not looking for exact copies in terms of pre AND power amp sounds. just preamps. I've compared the preamps of the real amps spectrally to the preamp responses of the axe and with TM they could be so close the difference was negligible, once Fw 10 gets here and the dials are exact to the real amps it should get even easier.[/color].