I heard the 6120CGP for hours and hours at the Chet convention, where it was played through a pair of Gretsch amps. The Executive sold the day before the guitar was introduced, so we made do with a Playboy and a Variety.
(Hear that combo here and here.)
The Gretsch amps are the best amps I've ever heard, flat period. Like dub, I've played through Victorias and they're fine amps, but didn't strike me as worth the money.
The Gretschs, made by Victoria, for whatEVer reason (and we go round and round about that), may not be WORTH the money, but I'd PAY the money if I had it. That isn't true about any Vicky I've tried, and the Gretschs are even MORE expensive.
My favorite is, naturally, the top of the line, the Variety 3-10. The Executive would more than do in any kind of Gretsch pinch; the Playboy fails me only because it lacks reverb and is voiced to sound best pretty cranked. (The other two are lush and fat with plenty of headroom in the clean zone.)
You know that the stereo on the CGP is bass-treble - that is, the 4-5-6 strings to one amp and the 1-2-3 to the other. (It's not neck pickup/bridge pickup.)
If I was voicing up a pair of amps for that, I'd use two different amps that uniquely flattered those ranges. Different reverbs in each will create a fascinating, complex, and lush soundfield, and you can tweak tones on each separately to bring each range into focus.
And better two amps than a single stereo amp (if anyone makes one), so you can play with cab positioning and make your stereo field as wide or narrow as you like.
The Blues Junior is a nice amp, but for my purposes not a great one. It doesn't come anywhere near the top of my mind for fingerpicked styles. Just not BIG enough sounding, not enough cab.
You need something to bring out the thump in the low end. Deluxe Reverb, maybe...but you might want to listen to big guns like the Twin or the Super. Used Music Man amps from the 80s are punchy, lush, articulate, and have great reverb.
Don't be afraid to try amps with 15" speakers either - the Executive, Peavey Delta Blues, etc.
I'm also required to mention my love for 60s Ampeg Reverberockets. A distinct voice, very flattering to Gretschs, and great reverb. They lack low-end, though, and would not let your CGP thump as it ought (though they'd be great on the high end).
My other favorite expensive amp is the Matchless Lightning Reverb - that for the high end of your guitar and an Exec or Variety for the low end (and either one when you're going mono) would make some kind of ultimate setup!