I will be blunt, if your wife gave you the go ahead for up to $500, buy the more expensive upgrade now because you will be able to talk her into a less expensive one more easily later than vice versa, at least that is my experience. But I am also really wanting to hear what Magnequest would do for my own amps. I have them in my Dynaco but not my SET amps. So I would head that direction but of course you should probably wait to hear from someone who has done both, I haven't done either!!!
Paul