To be honest, I can't help you based on how you phrased the question: you collect both guitars and amps, and perceive them, at least far more than me, as an investment vehicle as well as musical instruments.
I don't see my stuff that way - I buy them to play, and fully expect to die before selling them, so my estate will reap any actual value.
But I don't see the PRS guitar gaining in value faster than the amp, in this particular case. But...what do I know, I don't spend any time researching such topics. Which would make me a lousy investment counselor, over time.
So for me, it would be a case of: assuming equal value, do I need/want that amp, right now, more than that guitar, right now?
Actually, if it was me, I'd keep the amp (unless I really didn't like it), and save up a bit and buy the guitar too, if possible...