Importance of input tubes to sound quality?


I've been running  good pair of Mullards in the input section of my LSA Statement integrated for almost two years now and was contemplating rolling them for a really good pair of 6922's. The Mullards replaced the stock tubes and made a slight difference in the openness of the stage, though that may have been confirmation bias.

Before I drop several hundred dollars on a pair of tubes, do different levels of input tubes really make a difference in sound? Can they do so on a physical level (as in, is it physically possible for them to do so)?

Ditto for the stock 12AX7's in my Jolida phono stage.

 
128x128simao
Of course they do but I'm sure there are a lot of folks who just aren't tuned into the degree of difference they might make. Some times it is fairly subtle and sometimes it is obvious depending what your equipment/set up is and how developed your listening skills have become. Tubes have a basic sonic signature. If you know how you want to change the tone, etc, of your present amp just tell folks what you are presently using and what you want to get and you should get some specific recommendations. 
Okay. But how does the sonic sig of input tubes differ from that of output tubes?
An input tube is just a "baby" output tube, It takes the signal and increases the voltage, same as an output tube.
Tubes are made with different materials, spacing ETC ETC and thus they all sound different.
Same as how cables or capacitors sound different.
A good basic read is "Joe's Tube Lore".
While you're results may vary from his it is a good starting place.
Read that first and then let's see if you have anymore questions.
Most of all have fun with it and enjoy.
If the small signal tube is used in the amplification stage (pre driver) of your integrated amp then it will have a significant impact on the sound quality. I've had better results rolling driver tubes than output tubes. 
Simao, based on your original post I also was hoping to get more feedback on the relative benefits of rolling driver vs. output tubes, such as that provided by brf.  Good thread!  

I use a tube all pre with a SS amp. While I realize the pre has driver and output tube stages, within the context of my entire system I consider the preamp tubes to all be driver ones.