Phono Inputs...what can I use them for?

I would also say no for the same reasons, but would more forcefully say that the RIAA equalization COMPLETELY screws up the sound. You should not use them for anything other than a turntable. You could consider getting back into vinyl, you know!

I think Viridian's and Stan's suggestions are good. To explain what Elizabeth and I were saying, generally a phono stage is used to accept a very low level, comparatively weak, signal from a phono cartridge and amplify that signal. Thus , there is an amplification stage in the phono stage that, were you to feed it a signal that is too strong, would overload the unit. The RIAA equalization is also built into a phono stage--records were intentionally cut with reduced low frequencies so they could be cut on the record and played back by a stylus (I'm oversimplifying--I'm sure other frequencies were intentionally changed during the cutting of the record)--the phono stage has a built in equalizer to attempt to restore the frequencies to what they were on the master tape. If you play back a source like a CD that was not "reverse equalized" like a record was, it will skew the frequency response of the music on the CD.