I don't know about the Speco's as I don't have them but I know someone who is knowledgable will comment.
As for the PJCCS, I built mine without it and then added it in. Two different animals, in my opinion. The mids and especially upper end seemed smeared a bit "standard" but became much clearer when the PJCCS was added. Overall, the tone seemed to soften and become more natural, too. However, I have to say that I didn't spend too many hours with it out, so it may have been a bit of the natural bloom from burn in. I think for $35, you can't go wrong with that.
I also switched to the Mullard tubes, which I think many folks find to be a good tube if you can find them.
Finally, I am intending to add a second set of output jacks to mine (I like to bi-amp with my 6CL6 SPUD amp). I have heard it is best to use a resistor between them but I believe Q did his without the resistor and said it sounds great!
Best of luck to you and enjoy the project.
John
John Kessel
Hawthorne Audio AMT K2 Reference Speakers
Paramount 300B w/MQ All Nickel Iron, Mundorf S/G 5.5 uF, and Vcap Teflon .1 uF
Auralic Taurus Preamp/Auralic Vega DAC/Auralic Aries Streamer
and lots of room treatments!