The Expert drums are very nice, but the 2509 and 2509n reels work very well for 4x5 on the CPE2. I think some people also develop 5x7 and 8x10 film on the CPE2 in paper drums but I've no experience with that.
I'd love to have a CPP or CPA, but not for the price difference. My CPE2 suffices and does very well for what I do.
I only shoot 120 film (645 and 6x7) so I really don't need anything bigger. I also only shoot about 5 rolls a week...sometimes less depending on the time of year. Right now it's closer to 8 because of the bluebonnet season here in Texas.