Small or big tubes/valves for pre amp ?

I buy from Andy also.
Thanks for the compliment on the 864-SR
I also replaced the coupling caps on the 864-SR with Jupiter copper foil....
Not cheap , but Very Nice sounding. I have some JAN CHS-VT-231- 2 hole black plates that are my favorites , but still they lack bass
I like the JAN-CRP-6F8G-VT-99.

Just to clarify, I like a bit more detail than I hear at the moment with my setup,  but don’t want the details thrown in my face so to speak, just want to be better able to follow different instruments in a classical piece for example, not detail for detail sake ;-)

@gryphongryph , I listen to classical almost exclusively, I hear what you're saying. Good soundstaging and 3D imaging are important to me with orchestral music. And I want enough detail to hear the instruments in a realistic way. 

I spoke to Don Sachs and I've read many user reviews; his preamp would be perfect for you. He said it's very transparent with a black background. I didn't go with his preamp because an Audio Note came up for sale at the time.
  You should check out some of the threads related to the Sachs preamp.

Using 6SN7's in a cathode follower design, be prepared to do some tube rolling. There are many different combinations of tubes that will get you the desired sound. I love tube rolling, but it can get expensive with NOS.

@grey9hound , I'm using Tung-Sol JAN-6SN7GT, black oval plates/ black glass (1940s). It took Andy a while to find these tubes. He's such a great dealer and asset; I put in an order for the T-S's and he called me when he procured them. They're one of the "holy grail" tubes.
   Before that, I was using KEN RAD VT-231 1940's in my preamp (also purchased from Andy). All his tubes are low-noise and I've never had any microphonics (knock on wood).

You're using Raytheon with an adaptor? What's the sonic signature of these tubes?

@gryphongryph I’m also a fan of Van Morrison. When I swap tubes, I use cut 2, Philosophers’ Stone from Back on Top, as one of my references. On this cut, he’s very close mic’d.

I have a tube preamp (6922’s) with a tube DAC (12AU7’s) along with a Class A solid state amp. I’ve probably swapped about 20 different brands of NOS tubes. Depending on the tube (and cabling), his voice on this cut can be hot or recessed or just right.   But, more than naturally reproducing a male or female vocalist, how is the PRaT?
Does a snare drum sound crisp?  It's a challenge to balance everything out.

I used to enjoy NOS Mullards 12AU7’s. Then, I went on a binge to seriously clean up the power to my rig. After doing so, the Mullards sounded overly warm with low resolution. It turns out they were masking a problem that I had with dirty power.

I totally agree with lowrider57.

That’s a generalization that large tubes sound better than small; it depends on the implementation of the component.

It would be ideal if you could audition a preamp in your system before purchase. Are there any audio clubs in your vicinity?