Where to buy NOS 12AX7's?Which ones?

Fellow 'Gonners have said that I should get the tube mod for my new/used Mesa Baron but it was just re-tubed with stock 5881'sand I want to hold off and use 'em for a bit (also short of cash!).But I was told that most bang for the buck roll would be the drivers.Any suggestions which ones and where to get 'em at a price that won't make me faint?How long should they last?Also still taking suggestions on power cords.A number of folks say heavy duty Belden cheapies will do it others have there fave's.Don't know what they sound like but have respect for the Mappleshade/Omega Mikro folks and Hovland and thinking I'd go with one company for all my needs.How about MIT Z-cords?Think that some of the prices out there are BS.I have a pair of german horn loads (Ehodin)now but might get B&W,Audio Physic,Maggies etc so I need wire with bang for buck that isn't specific to to a speaker.Also have SS Mac 712 and might go tube there.Old MIT first generation tube terminators have been suggested.Need lot's of input so don't think me overly neurotic (yeah right!) if you see these same Q's on another thread.
Cheers!