Newb Tube question

Caveats, in relation to "tube rolling".  First, in my experience mediocre sounding gear does not become wonderful sounding gear via tube rolling.  If you don't like the sound of your preamplifier, don't expect to transform it by buying expensive "rare" tubes.  Maybe that which is already "good" can be made a little better, at best. However, with some understanding of circuit design, sometimes changing a capacitor or the basic topology, here or there, can make a big and permanent difference.  Second, keep an open mind.  Sometimes you will be surprised by a Chinese or Russian made tube compared to an NOS Euro or US made tube.  Also, in some rare cases, you can substitute one TYPE for another which can be a big step up, but you need to know that the replacement tube will be connected to the circuit the same as the discarded tube.  Any time you can get rid of a 12AU7 or ECC82 in favor of a 6FQ7 or 6CG7, you will be happy, but in some cases you will need to do some soldering.  (6FQ7 and 6CG7 are electrically like a 12AU7 but filament current and voltage and connections need to be considered.)

I suggest trying some 6FQ7s with good paint. Conrad Johnson used them back when they were in production. Matched pairs $25-$50.
RCA sounds better than Sylvania to me.

To avoid a lot of disappointment and frustration: just follow tomcy6's advice.     

AAAAAHHH Tubes :-) They are like little bottles of electronic wonder and joy. However, being new to tubes in 2020 is to embrace the term "made in Europe or Asia" Of course anyone with an old warehouse and a tube tester is now on the tube bandwagon and is a expert. My point is that there are many crappy pedestrian sounding brand new tubes out there so it pays to do as much research as you can by yourself and take the time to learn why tubes work and what they do. I agree with lewm that tube rolling is better with better sounding gear, so dont worry about buying a $180 tube to put in a $150-$300 unit. Stock tubes are fine with these products. Where Andy At Vintage tubes comes in is when you have a special sounding unit and your looking for "real new old stock tubes from the 50's 60's 70's" to really bring out the best. That is special.

Matt M

@lewm 

First, in my experience mediocre sounding gear does not become wonderful sounding gear via tube rolling.

Beware, the corollary is also true - a bad tube can make a great amp sound average.