When you get to the Audioasylum.com website that was mentioned above , go to a part of it called Joe's Tube Lore . There you can find a rather exhuastive comparing of the small/input tubes . It was done using a different preamp than yours but the difference described between the tubes can be helpful . It's a nice starting place .
For me , the small/input tubes made the biggest difference and are usually much cheaper than the large/power tubes . They also can be changed with less hassle as they do not require that you reset the bias like the large/power tubes .
Good luck.
For me , the small/input tubes made the biggest difference and are usually much cheaper than the large/power tubes . They also can be changed with less hassle as they do not require that you reset the bias like the large/power tubes .
Good luck.