I used to stuff bits of this or that together in one do-it-all box just to see. You could build a speaker cabinet for the purpose of recreating fine hifi music: Woofer/midrange, tweeter. Add the appropriate electronics to re-create hifi music. And speakers out both side so as to disperse the sound nicely like a stereo system. Then you add the guitar electronics and mix that in so that it eq's like a guitar amp should, with its narrower and tailored sonic profile. I'd guess the little modeling amps do some of this to be super flexible. Or the acoustic guitar amp and PA combos for gigging in the park and so on. Back to your project: The guitar section can all be tube if you want, but it is filtered to sound like a guitar amp once it comes out the hifi speakers. But you can put a separate speaker in there for the guitar to sing through. Now you have invented the El Camino, a car that's a truck, or a truck that's a car! But that's ideal for neither! And your amp is getting heavy... I agree that the "CD" input is something a guitar purist won't use unless his boom box or stereo isn't nearby, and lets others think they can use a guitar amp as a PA. No real harm being done here. Some of those big old console stereos I have seen with "guitar" as an input.