know you are looking for 5150 input, but just thought I'd add my 2 cents. I have all JJs in my 2-ch Dual Rec, and I have no problem whatsoever with the tone being dark in any way. I actually boost my treble less than I did with the stock tubes. Here's my setup right now.
GP (gold pin) seems to give a little bit more mids than the normal version, also seem a bit smoother in the high end.
V1: ECC803S GP: A nice warm & round clean w/ a nicer sparkle
V2: ECC83S Std GP: Enough gain for orange, but still nice and warm
V3: ECC83S HiGain GP: Only gives a bit more gain, but I have to use the gain knob less for the same saturation.
V4: ECC83S Normal - for FX loop
V5: ECC83S Balanced - phase inverter
Overall this setup really improved the clean, and added a much nicer mid section and smooth the fizz compared to the stock tubes. I also have the JJ 6L6GCs in the power section which I think sound great, my fav 6L6 tube out there.
Some people use the Higain in all V1-V3, but I really only wanted the gain boost for red channel, so I only have it in V3. After using the standard and gold pin versions, I think the V1 is really the only spot that truely benifits from the gold pin. It's not worth the extra dollars for V2-V3. But i think the ECC803 is def my fav V1 tube at the moment.