Alright If I cover anything that has been said sorry, I didn't read everyone else reply. I have owned and been working on MACS for the last 10 years(yes before they were popular to some extent). My advice to you is this...
If you want to run those programs without major bogging or crashing, get a dual processor G4 or if you can afford it G5. the dual processor is made for programs such a FCP and Photoshop. A single would work, but you will get much better proformance from these types of programs wih a dual.
Load that fucker with as much RAM as you can. those programs strive on RAM to opperate flawlessly. You can't have enough. OSX (panther prefered), it has a couple of more features than jaguar and is a lot more stable for large file transfering and editing.
My advice in a nutshell, get a G4 1gig or more dual processor (if your wallet can afford it) or G5 AND ATLEAST A GIG TO A GIG AND A HALF OF RAM. I cannot express how important the ram is. Almost more than the processor speed. Partition your drives to allow a good size (20-30 gigs min) for scratch space only. It would be wise to spend the extra money now and get the biggest system you can so later down the line you can add a little here and there and not have to buy a new setup in the near future. If you can find a good deal on a used(or new) G4 1.42 dual proccessor, go that route. the G5's are nice ( i have 2 at work), but not nessasary. PM me if you have any more question. I work for Warner Bros. Studios and use Macs for a living each and everyday in the real world for photo/vector editing and large format printing. i have owned at least 8 different macs (from the original beige G3 to the newest G5) I can tell you the ins and out of each and hopefully steer you in the right dirrection.
matt