Djinn1973 .............
That is a hard question(s).
I am not up on prices, they change all the time, and ebay may be a good source of info.
To increase reliability, have the amp checked out to make sure the transformers are good, caps are good, and then retube and reset the bias properly. Clean and lube all the pots, and give the amp a good once over. I went back, and after hearing it with my own guitars I decided against buying the Voodoo.
On a side note, before I left the store I picked up a 12AT7 EV. I used it to replace the (Fender special design) 12AX7A in my hybrid combo. When I fired up the amp I was shocked; the amp was quiet, responsive, and best of all it sounded fantastic. Every one that has heard me through this amp (after I put the 12AT7 in) has made some positive comment about my tone.
With out having read your tube primer, it never would have occurred to me to replace the preamp tube with any thing other than a 12AX7.
Thank You, Myles.