I put an orange frame D120F in a Headstrong Lil King, and couldn't get it out of there fast enough. Super nasally...I just don't think that a 12" JBL in a Princeton size cab is ideal. I ended up with a ceramic Tone Tubby, and the amp really sounded like a little Twin. I eventually sold the amp, but recently picked up a PRRI. After plying it for a few months stock, I made a 12" baffle, but realized pretty quickly that the 10", for me, sounds perfect with that circuit/in that cab. So, now I'm looking around for an E110 or maybe a Weber Cali, or possibly even a Gold. I'm just wanting super clear and extended frequency, but not necessarily JG. I also use a 15" extension cab with the Princeton sometimes that sounds huge. The 10" plus an extension cab is very full for a small amp.
I just discovered Milkman Sound Amps. He makes a 20 watt Princeton type amp that is very heavily Twin inspired, as he builds mostly pedal steel amps. It's expensive, but I'll bet it would be great for a lower wattage JG tone. Also, the Allen Sweet Spot is a beefed up Princeton that can take 6L6's...most seem to find it much more articulate than the average Princeton. He sells them as a kit option that is not too expensive.