Need advice on CJ preamps

Pops, you may already know this, but the Premier 14 uses a cathode-follower output, so its output impedance is 'low'.

1. When one can buy NOS Mullard 6GK5s for $15 per 5...
http://www.ebay.com/itm/Vacuum-Tubes-6GK5-MULLARD-UK-5-NOS-NIB-/330602242584?pt=Vintage_Electronics_R2&hash=item4cf96de218
...why switch to another tube?

2. The Premier 14 uses only one coupling cap per channel in the signal path, a 2-times-2uF pair. I suspect they're c-j's 'styrenes.
3. Replacing these output couplers probably would be quite easy, and one wouldn't necessarily need 4uF, either, depending on the input impedance of the poweramp.
4. The PS regulator-output cap is a 2uF, and that too would be easy to upgrade.

I suspect anyone doing these upgrades would end up with a VERY-fine-sounding linestage preamp for not much money.
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Dopogue, probably you're right about the inherent quality of the 6GK5; c-j switched to the M8080/6C4 in several preamps several years ago. As it too is a 7-pin single triode with 6V. heater, I wonder if it's a drop-in replacement or perhaps doable with only a resistor change or 2. I know only enough about circuit design to be dangerous, so this isn't a recommendation.

...but it is an encouragement to Jaxwired to consider one.

I performed cap upgrades such as I mentioned to my c-j MET-1, their now-discontinued 6-channel preamp, and the sounds improved to such a degree even this tin-eared audiofool readily heard them.
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