I was looking on online and I saw a power amp. I was just wondering, is it just a solid state amp? Or does it amplify power or what?
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A guitar amplifier actually consists of 2 sections: The Pre-amp and the Power-amp. Mostly they are build in one single unit (tops or combos). but you can get them also as 19" Rack-units, preamp and poweramp seperately. this fact gives you a lot of possibilities to combine different preamps to different poweramps.
to describe it very easy: the preamp section is responsible for the sound-settings with all the parameters (treble, bass, middle etc....) and the poweramp just brings this preamplified signal to the speakers.
a poweramp powers the speakers

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If you coupled that with a SS preamp, then it would be. However, the product you linked to is only the power amp. You would need to use that poweramp with something like a Marshall JMP-1 in order to have an entire amp. If you're only using the power amp, you won't be able to sculpt your tone with preamp tubes, EQ's, gain, etc.
Do you wanna use that as a guitar power-amp???? hm....your choice. This one is actually made to be used as a PA Poweramp in combination with a mixing console, which in this case is the "pre-amp" with all the equalisation etc. but sure, you can use for whatever you like.....

If he likes the sound of a certain preamp and doesn't want to color it, a high end SS power amp is the way to go.