keyboard through bass or guitar amp, or bass or guitar through a keyboard amp?

[kayak]

Which one of the scenarios would give the best results:

 

1. Switching between bass guitar and keyboard using:

a. a bass guitar amp (Markbass LMII)

b. a keyboard amp (make a recommendation)

2. Switching between guitar and keyboard using:

a. a guitar amp (Vox Valvetronix VTX)

b. a keyboard amp (make a recommendation)

 

Type of music, 60's pop rock/british invasion.

[rovito]

The Roland KC550 would work well.

[pogo97]

If I was in that position, I'd buy a good bass amp and run the keyboard through the PA.

 

Alternately, and I haven't tried this amp, a Traynor K4 which has the much-in-demand-for-keys stereo and is, by all reports, big and loud with a tube preamp. I've had a couple of keyboard amps (currently a Motion Sound 200s) and they would absolutely not serve for bass; not enough bass and too clean.