What are the best tubes for a VTL TL 2.5 Preamp?

Will changing tubes really make a difference over the stock tubes? Which, by the way are made in China. My VTL uses 2 12AU7's and 2 12AX7"s. Will different tubes and brands make any difference in the sound? Thanks for any input.
There are major differences in tubes, both in 12AU7 and 12AX7 types. In both cases my favorite is Telefunken, especially in the 12AX7 type. I think they build the best 12AX7 ever made.

Will different tubes and brands make any difference in sound?

That depends entirely on your system and set up. Your system is not posted here at Audiogon, so I don't know your other components or room set up.

Assuming the rest is equal to your VTL 2.5, I would say yes, premium tubes will be an audible improvement in your system.

Is it worth the investment? That is another matter, especially when discussing Telefunken, which are expensive.
I can say that when I replaced my amp's stock China 12AX7s w/NOS RCAs, the amp immediately sounded MUCH better. And I'm not talking subtle differences here. I would do some research before buying, but you definitely want to get those Chinese tubes out of there.
I agree with Albertporter, and recommend Telefunkens. There's a lot of crap and bootlegs out there. I also recommend Andy at Vintage Tube Services as a source!
I retubed my VTL 2.5 with NOS Mullards but mine uses 12AU7 and 12AT7 types, 2 of each. I bought mine new in 2005. You may have an earlier version that used 12AX7s. The sound quality improved noticably. The tonal characteristics became richer,sweeter and more realistic without any loss in detail or resolution. It cost me about $140 for all 4 tubes and would recommend it. I may try Telefunkens alone and in combo with the Mullards just to experiment. It's fun but you need to let them break in awhile to get the true sound.
Like Noble my VTL 2.5 uses 12AT7’s and 12AU7’s. I have tried the following 12AU7’s Golden Dragon, Ei, CIFTE and Telefunken. Except Golden Dragon, all sound pretty good but it was dependent on what 12AT7’s I was using at the time. My advise is to shop around, mixing and matching is a fun way to spend a afternoon.
Thanks for the responses. My VTL does use 12AT7"s and not 12AX7's.
By the way, which has more impact on the sound the 12AU7"s or 12AT7"s?
before investing in expensive tubes, ask the manufacturer if the circuit is tube sensitive.

i have been told by at least 2 manufacturers that the brand of tube will have a very small impact upon the sound of a component.
My Lamm LL2 Deluxe is quite sensitive to tube swaps (using both 12AU7 and 6922). My previous First Sound Presence Deluxe II preamp was not as sensitive as the Lamm, although tube swaps did make a difference in the system's sound.

I agree that swapping some less expensive tubes would be a good way to proceed before spending large amounts on NOS tubes.

By the way, there are many domestic NOS 12AU7 tubes that can be excellent...Raytheon and RCA 5814A come to mind. They run about $40/pair on E-Bay, and they sound quite good.
i suggest that you consider ge 5814 black plate along with the other selections.

"By the way, which has more impact on the sound the 12AU7"s or 12AT7"s?"

I'm not sure which has more impact since I swapped both at the same time. My guess is that they both do since the signals flow into both sets (1 set for input and 1 for output).