Mcintosh C2600 preamp tube upgrade


I recently added the new McIntosh C2600 tube preamp to my system. It's paired up with the MC452 power amp along with Sonus Faber Elipsa speakers and Transparent interconnects/speaker cable.
I"m looking for some guidance with regard to upgrading the tubes in the C2600. Should I, or shouldn't I ? 
Also, what brand should I look for and where should I buy them. And finally, is this a diy upgrade or should I have it done at a audio shop? 
I appreciate any guidance all you audiophiles can offer
ad48170
Interesting, I did not know that there was a 12ax7a.  I use 12ax7's in my non Mc preamp.
Jetter,
I found somewhere on the web that the "a" at the end of 12ax7a meant that it had a wound filament.  Not sure what that means to the sound quality.
Hi ejr, I found the same.  In the short description I read, it mentioned the filament helped reduce microphonics.  I am not that experienced as neither my tube amp or pre has ever suffered from microphonics (that I noticed anyway), but I would have never guessed the 12ax7 in general would be prone to it. 
I know this is off topic, but has anyone compared c2600 with c52 as paired with mc452? How much difference is there? Is it clearly audible? Which would you recommend for classical music with VA mozart speakers? 
I auditioned both prior to purchasing the c2600 and to my ears the c2600 paired with the mc452 is a perfect marriage. IMHO tubes and classical music go hand in hand yet when I listen to jazz the 452 has the punch jazz begs for. As I recall the most significant difference between the c2600 and the c52 was the mid range. 
My speakers are Sonus Faber Amati Futura's, but I would assume my conclusion would probably be the same with any good high end speakers.