sharkbait130 and TomB,
Thanks for the input guys. My 450 has been acting up with a weird noise on rare occasion. Unfortunately (fortunately), I only have the one rig and I'm gigging heavily nearly every weekend, so I can't get it into the shop with a backup. I've been looking at the Ampeg D-class offerings but don't have one nearby to audition in person. I've seen a PF-800 available near me used, but will have to play a few more shows before I have the cash for it. Hopefully, with 2-3 shows every weekend, I'll have it saved up before something more drastic happens to the 450. Depending on how I like the PF, I might end up keeping the 450 as my backup.
Again, thanks for your opinions and experience.