I'm running an '87 Peavey VTM-60 through the matching 4x12 with Celestion G12k-85's.

Right now I've got the headshell in my garage, in the process of being painted and then clearcoated.

I plan on clipping the bright-cap, but I also thought it might be interesting to test out a pair of tubes I bought.

Right now the VTM is running 2 GT-6L6GC's, which were apparently new when I got them but I sort of doubt it. I was just wondering if swapping them for a pair of unmatched Sovtek 6L6-WXT's (wxt?) would be safe for my amp and if it would have any effect on my tone at all. I'd prefer for a lower-mid heavy tone, perhaps a bit fuzzy, with some bite. I've got a Ibanez STL to tweak most of that.

I forgot what the specs on the box were but they seemed to be reasonably close together. Also, my VTM has no bias adjustment, and requires a slightly complicated mod to put a bias pot in... Is this a sign that it can "take a beating" or that it's probably quite sensitive and requires matched tubes?

I remember reading an article saying matched/tested tubes were a ploy made by RCA and GE, Philips, etc etc to promote their vacuum tubes back in the day....

Thanks in advance?
I've got Sovtek 6L6WXT+s in a 1983 Peavey Encore 65, which replaced the original Peavey-branded (Ukrainian-made?) tubes. It gave a little more edge, but it was subtle. You get more of a tone change with a tweak of the Presence knob than a tube change. Those weren't matched and I didn't rebias. It's been over a year and I haven't had a problem.

The matched tubes thing is really a symptom of modern low-quality tube production. Back when, tubes were held to high enough standards that all tubes of the same model were "matched." Nowadays the plate current draw and such vary wildly, so people match them. However, unmatched tubes won't make much of a difference. In fact, I've known people who deliberately mismatched tubes to increase the second-order harmonics. (I couldn't hear the difference, but they liked it.)