I realize this is a huge subject, and then when you get into tone it's
even deeper but I'll go ahead and ask.

When it comes to audio/PA speakers, you generally want 1X to 2X of the
power amp watts relative to the rated wattage of the speaker...it's
better to have too much power than not enough.

How does this apply to guitar amps and speakers though?

My guitarist wants to get some new speakers for his Genz-Benz cabinet,
the stock ones are 12" (it's a 2 x 12" cabinet), some sort of nameless
things with square magnets (CTS perhaps?).

We're considering Celestions of course, and perhaps some of the
Emminence offerings.

The rig he has uses a two channel Peavey 50/50 tube amp (it uses
EL84's in each channel's power section), which puts out 50 watts RMS
(I'm not sure of the distortion spec for that rating) per channel.

Ideally we'd like to run each channel into each speaker of the cab;
you can run the cabinet as one channel/mono (8 ohms) or two
channel/stereo (two 16 ohm loads).

The music is rock guitar, lots of loud chords and searing lead kinda
stuff, but also some clean, lower volume stuff...basically the full
range of tones.

I kind of like Vintage 30's, but they can be a bit bright, "reissue"
Greenbacks are another choice he is considering, as well as the other
Celestion models (and then you have the Emminence drivers, which sort
of follow the Celestion power ratings).

Anyway, the Greenbacks are 25 watts I believe, the Vintage 30's are 30
watts, the other Celestions tend to be rated around 75/80 watts.

I've used this same power amp (one channel) to drive a single Vintage
30 (in a 1 x 12" cabinet) with no ill effects, but it wasn't used all
that often and for all that long...also this was at 8 ohms (the amp
offers a selection of impedance settings...4 - 8 - 16).

I guess getting to my question...is it ok to run these speakers with
more watts than they are rated for with a tube power amp in a
distorted guitar setting?

I'd think this may be harder on the speaker than full range, clean
audio through a PA or studio monitor speaker.

On the other hand, a bit of speaker breakup would be a cool
thing....the Peavey itself is a bit clean, we're getting the
dirt/distortion from a modeling preamp that he's using.

Anyway thanks for any advice, I don't know much about guitar speakers
and amps, since I'm not a guitar player.

Analogeezer