Hi mnewland1,
Do you know which type GTs, Chinese, Russian (EH or Sovtek)? The reason that I ask is that they all have different sound, and if you like the sound that you have now, or do you want a change? Typically, the Chinese are warmer clean, and less edgy for a smooth distortion. The EH are bright/sparkly clean, with edgy distortion. The Sovtek are more neutral clean with fairly edgy distortion.
I personally like GTs, and if you like the sound that you have, stick with them, but I am always trying different tubes. If the GTs are Russian, then the current MB 12AX7 might do quite well in all positions. The current MB 12AX7 are JJs, but thoroughly tested to weed out the bad ones. If the GTs are Chinese, you might want to try some Tung Sol.
The only real way to know if any particular tube suits you is to get a few different ones and try swapping. Preamp tubes are plug and play. The guitar and amp used will also make a difference as to the sound that you will get.