Here is a suggestion: every day when you are about to listen to your 350, pay your piggy bank for the privilege some small amount. Enjoy your 350 immensely along the way, and when the piggy bank has enough to send to Frank for the upgrade do it. While you wait (that's the tough part), remind yourself of how impossible it would be for the amp to sound any better. When the 400R comes back, enjoy your astonishment.