I just finished putting 'new' tubes in my Boogie Simul Satellite and regarding what kind of tubes to use I will echo what advice I havee been given. They type of tube does not matter in terms of type. A 12AX7 or a 12AT7 or 12AU7 will all sound different, but the important thing is what YOU like, what sounds best to YOU. I would recomend trying a whole bunch of tubes in there and switching them out to hear the difference in tone.
My friend gave me several older tubes he recovered from various tube based equipment, 2x 12AX7A 2x 12AU7 and 2x 12AT7's. The 12AX7A's(labeled Lowery Organs) are made by GE or RCA back in the 60's and sound killer, the 12AU7's one is a British Dynascan (made in Japan) that was used in testing equipment, the other is a Sylvania MAde in USA and it is burnt as hell and breaks up very fast. The 12AT7's, one is marked CHY Hytron, and the other is another Dynascan. The tubes my tech placed in there are new Sovtek 12AX7WB tubes, which have a shorter plate and are larger diameter tubes, these sound very different as well.
I tried differnt cominations of these tubes in quick succession to determine which i liked best and in what position. I highly recomend that you take the time to do the same. The same 5 tubes may sound different in different positions. Try having your tech switch them out if you're not comfortable and crank the amp up on the spot. Look for at what point do the tubes break up, how much head room you have, the tone, if the tubes sound brittle or full, etc. You will hear a difference. Choose whichever ones sound best to you.
I settled on a 12AX7A in the first position which I assume is the signal preamp, and the Hytron 12AT7 in other position (tone?) and it sounds killer.