At least one key factor will be finding a unit in good condition. I have a early-80s Counterpoint pre and it performs well. Actually, repairs for any of the brands you seek are not much of an issue. Both the SF and Counterpoint will be low priced due to their manufacturers being out of business. However, each is supported by repair facilities operated by the same people that manufactured them, so it shouldn't be a worry. In fact, I had my pre restored by Mike Eliot and it has proved trouble free. Also, it's easily tweakable with tube rolling and shows the characteristic of whatever tubes I try--a sign that the pre is transparant enough to show such differences. Another thing to consider is that you may have matching issues with your amp. I have a Counterpoint pre and SF amp and can't get the volume knob much above 9 o'clock before things really take off! YMMV as amp gain/effeciency of speakers will dictate that interaction.
Haven't tried the Joule, but their power amps are something special.
I can comment on sonic differences between the SF and Counterpoint "house sounds"--Counterpoint adds body with more lushness while the SF is more precise and better extension at both ends. Either one gives a good showing of why tubes rule. In short, I think you're barking up the right tree with any of the brands you mention.
Haven't tried the Joule, but their power amps are something special.
I can comment on sonic differences between the SF and Counterpoint "house sounds"--Counterpoint adds body with more lushness while the SF is more precise and better extension at both ends. Either one gives a good showing of why tubes rule. In short, I think you're barking up the right tree with any of the brands you mention.