I currently own a solid state (Crate 350Watt head with 4x12 cabinet) and tube (Fender Twin - 85Watt, 2x12) amp for guitar, and a Carvin 1800W solid state PA amp for voice and keyboard, and many other amps along the way.
Set the guitar amp to its clean settings and the keyboard should sound fine. The tube amps have a really nice distortion when they start to overload, which sounds great with guitar. The solid state amps often try to emulate tube distortion with special circuitry. Crate call theirs Flexwave, and it's not bad but it's not as nice as real tubes. The Fender Twin has a real spring reverb and it's way better than the dsp reverb in the Crate.
None of that should concern you if you want a clean sound with a keyboard. Tube or solid state are both fine. Solid state will usually be cheaper and lighter.