Upload & Sell: Off
Glad to hear this was useful for you.
Two added notes...
First, that you're contemplating the hardware option another great Mac resource can be found over at Bare Feats. This exuberant bunch of folks just love getting a hold of the latest Apple gear and storage mediums and then torturing them with a variety of benchmark tools and, er, "Pro Apps" like Photoshop, Aperture, Final Cut, etc., and, if you're so inclined, hardware-intensive games. You'll find your iMac (and later models) on their extensive list of hardware tests and see how it fared against its previous and subsequent incarnations (like my iMac), and other Mac products like MBPs and Mac Pros, etc.
Second, (and I should have touched on this before) the reality is, Photoshop is going to tax not just your CPU and RAM, it's going to demand the most of your Hard Drives. And there are hard drive choices that will make a difference in how PS behaves for you that you'll want to be keenly aware of if you're going to upgrade your existing machine or purchase another custom-configured iMac or decide to outfit your own Mac Pro. Again, the maniacs at Bare Feats have done a lot of virtual try-before-you-buy testing with Photoshop, et al, and various HDDs for you to help you understand what your choices are and why.
Real World Speed Tests for Performance Minded Apple Mac Users:
(P.S. I have no affiliation with any of the links I have provided.)
BTW, if you end up playing around with the Tile Settings in PS for those panoramic shots I'd be curious if they helped make a difference for you. I've accumulated a lot of pano sequences over the years and have just never gotten around to stitching any of them together to see how it all worked out! D'oh!
Anyhoo, have fun with your solutions hunting!