These clips clearly tell you a little about Edge's amps. Fact is, most of his amps are "original" on the outside, but contain several replacement parts.
I guess what I am trying to add (and I am in NO WAY AN EXPERT HERE) is that I agree with Mick that all amps are different, like a pair of shoes. They all look the same perhaps, however much like a guitar, they feel or sound different. Also the fact that even though Edge's amps are primarily vintage AC 30's, even those are not really "all original" yet constantly shaping and reshaping part of his sound.
I'd say go with Mick's idea. Grab a delay, and sit in front of every amp I could get my hands on until you feel comfortable with the end product. Once you're happy with the sound, THAT is the amp you should get. ;o)
As quoted by The Edge in the following clip:
"The handle's been changed twice, it's had a new head put on a couple of times, ... I dont know how much of that (amp) is still original, maybe just the grill. The rest has probably been replaced at one point or another."
(see minute mark 3:20)
http://youtube.com/watch?v=ogrSq1I8Ecs
or for those who cant see the link:
youtube dot com slash watch?v=ogrSq1I8Ecs
As you see in the following clip, Dallas Schoo explains that there is someone that works on his temperamental amps full time. I'd imagine replacement parts are in abundance here too. ;o)
(see minute mark 1:08-1:26 ish)
http://youtube.com/watch?v=RGHqoUOT_z4
or for those who cant see the link:
youtube dot com slash watch?v=RGHqoUOT_z4
Cheers!