If the JBLs are the original D130's, you have a potent rig for sure. You also will have a rig that will stun small animals at 75 feet.
I own a 65 Showman, and it's a great clean sound; I run it through 2 Warehouse Speakers G12C in a Bandmaster cab to present an 8 ohm load to the head as it needs. Breakup? It sounds amazing, but by the time it reaches that sound level, you're over 110 dB, which is far too loud for any of our shows. So I get there with pedals.
The Celestion Gold 10 is only rated for 40 watts; I'd be nervous about having the speaker rating that close to the amp's rated output. The other thing is that the JBL D130's are nothing like a typical 15 - they have enough mid frequencies that you don't need a 2x10 with the 1x15. In fact as bob pointed out, you may find there's a bit too much "clarity," but you'll cut through the mix.
The two amps you're comparing are apples and oranges on 2 fronts:
Output - 15 watts is loud enough to play in most clubs and with a mic to the PA, plenty loud. The showman will dwarf the AC on a setting of 2.
Amp type - EL84 has a different sound to it than the Fender 6L6 - the chime tends to be a bit more "gritty," bright" and sounds great turned up.
Size - you can carry the AC15 in one hand with your guitar in another. With the showman/bassman head and cabinets, you'll need one of these (best band investment I ever made) 800 lb. Capacity 2-in-1 Convertible Hand Truck-CHT800P at The Home Depot
There's also some big shifts in those Fenders after 1968-9 that weren't necessarily for the better on the big amps. They were made to sound even more linear (no breakup) which may or may not be what you want.
So a lot of variables, but the big question will be what sound you like as well as how much gear you have to carry. I have several amps that I use as follows:
Recording at home: Fender Princeton, Bandmaster on 2, or Dr. Z Mini Z
Bar Gig, No PA - Bandmaster
Club gig with PA, Monitors - Princeton Reverb with Extension cab or Bandmaster
Outdoors with PA, monitors - Showman (closed back helps sound project since there's no wall to bounce sound back at me)
Hope this helps. Good luck!
nedorama Monkey Boy Studios
Summit 2BA-221, TLA-50
mBox Pro 3, Pro Tools 10.3.4, OSX 10.8.3
Radial JDI x 2, ProD2, ProRMP
'65 Bandmaster, '65 Tremolux, '65 Showman; '74 Princeton, '77 Princeton Reverb, Dr. Z. Mini Z Head & 1x12 Cab, pedals, George L's cabling
'65 Farfisa Compact Duo www.facebook.com/thetoysband