What is Overkill?
I’ve had unexperienced players come up to me before and say things such as, “Did you really need two amps just for a club gig?,” or something similar. The answer is yes, and the reasons are various.
What type of music are you playing?
When going to a gig with a setlist covering many different types of genres, it helps to have an amp which can keep up with the demands. Using a small practice amp will only get you lost in the live mix, and can end up sounding muddy and weak. You wouldn’t use a solid state Fender Frontman, which is something one may learn over time. Of course, if playing with an acoustic drummer, you would have to increase their on stage volume in order to hear themselves regardless of amp wattage. I’m not advising three full Marshall stacks, however, I am condemning amplifiers designed to be used as bedroom practice enhancers, and nothing more.
Using an amp that has a bit more clean headroom (15-45W) will give you a much more articulate, controllable tone. Easy for the sound guy to hear and mix, as well as making your band sound tighter, and more to the point, well-versed no matter the genre.
When you drive an amp to the point of breakup, and beyond, touch dynamics become less and possible, leaving you with a fizzy, noisy, hard to control ball-of-mud tone that cannot sway and lean musically with the rest of the band.
In having an amplifier over 15W or so, one begins to hear themselves for how they actually sound. There is no room to hide sonically the higher the wattage of an amplifier goes. All your technique and playing details are there, however, so are your mistakes. This reason in particular may be why many novice players don’t particularly like playing through louder amplifiers.
Quality of Repitition
The best way of keeping a predictable tone to what you are used to recording with, writing with, gigging with, etc, is by trying to use the exact same setup if and when you can. No one knows your guitar rig and how to make it perform at its best it better than you.
Do You Want to Sound Good?
If the answer is yes, refer to the previous reasons I’ve given as to why using what are technically classified as “low-wattage” amplifiers. Volume knobs go past 2, so use them as the were designed to be used! While yes, it may be a hassle carrying a pedalboard, amplifiers, and guitars to gigs, if you want to sound good, in most cases that may be the cost. I know from experience that this pays off; getting offers from serious musicians while members who weren’t as prepared are overlooked.
One must dress for the job they want.