OK, I'll weigh in :^)
You have what I consider the "good" power transformers, for what it's worth. The new Bottlehead iron is quite suitable; I think it is approximately comparable to the original upgrade, now long since discontinued. I don't know where the original documentation is - it re-purposed the old plate choke as a power supply choke, so it was a thorough upgrade. We can look around for a copy if you need it.
At 2 to 3 times the cost, the Magnequest iron upgrade is better, particularly if you spend for the nickel core output transformer. Not everyone is a fan of nickel, but most are - I certainly am.
Here are some more details; remember, all this is just my opinion - and I designed some of this stuff. These notes are my honest opinion, but a grain of salt might still be in order :^)
Original stock - 10 henry plate choke, output transformer with limited bass performance.
Original upgrade - 40 henry plate choke (Magnequest), built-to-spec output transformer of fair performance especially good in the bass.
"SEX upgrade" (current production Stereomour iron) - 20 henry plate choke, my own design output transformer with better than fair bass and better treble than the original upgrade. Note the choke has a tap for more inductance when used with a 45. $200
Magnequest Paramour upgrade package - a more refined version of the 40 henry plate choke, and a TFA-2004Jr output transformer available in M6, nickel core, or a pinstripe blend. It's no secret around here that I really really like the TFA-2004, especially in nickel. No, we don't get any referral fee! $400-600
The Paramount "soft-start" upgrade kit is also applicable, though there never were any instructions for this particular application. You have to have the PT-2 for it, too. $250
