Looking for Tube Pre-Amp Recommendations

I have Thiel CS6's but are not currently in use and I used a Musical fidelity 308cr full function pre-amp with them. Before switching to my current speakers, B&W 801 s-3, the MF 308 tamed the CS6's brightness in listening room. The 308cr, which is no longer made, but shows up often here for sale is the keystone of my system, no matter which speaker's I am using. It has a nice high frequency roll off, which sweetens up the presentation. Equipment may come and go but the 308cr pre amp is for ever, well in my system any way. Good luck.

I 2nd ZD with the Aesthetix & BAT. I had a new CJ ET3SE which I liked but didn't love. Also a used Shindo Monbrison could be had for $5k and an Aurieges for even less.

If you are keen to introduce tubes in the preamp, I recommend: -

TRANSCENDENT Grounded Grid Preamp

You can buy it fully assembled from the master or really enjoy yourself and build it from kitset.
(Or perhaps even get your local tube guru to build it for you...)

Even if you fully load it with the very best components that money will buy, including: -
A quality stepped attenuator
A quality switch
Additional RCAs if you need more than 3 inputs
State-of-the-Art diodes, capacitors and resistors
NOS 12AU7 tubes
Teflon/Silver wiring
Vibration control feet
Custom-built face-plate
etc. etc. etc.
...I doubt you would spend more than $3k

This little amp is an absolute blinder, combining frequency extension at both ends (1 dB down from 5 Hz to 300 kHz!) with sizzling dynamics and that magic tube 'palpability' that we all love.

Did I mention that it is STONE DEAD QUIET?

The web is full of rave reviews... Check it out.

http://www.transcendentsound.com/Transcendent/Transcendent_Sound_Grounded_Grid_Preamp.html

PS: I built mine in 2002 and still keep trying new upgrades to see how much more I can squeeze out of it!

2 recommendations: The first one requires patience and trust because if you can get your hands on one it will be a stroke of good fortune as they only appear on the used marketplace every now and then and to order one new could take several months... I'm referring to a Tube Research Lab: "The Dude" pre-amp. It is one of the very top most musical pre's you will ever know. It conveys the emotion and architecture of the music in a big holographic stage...
It's built like a piece of industrial equipment that essentially can remain "On" for decades at a time (mine is only turned off for other component swapping or temporary system shut downs like vacations, powercord swaps and such).
It comes SE or can be built balanced if you need it to be and also with 2 sets of pre-outs for biamping ( but double check this point because maybe not every one was built this way...). It is essentially 6SN7 based but also has a tube regulated power supply and can be had with a remote volume too...
Keep in mind waiting lists are very long if you still want to have one built (they are all hand made point to point wiring and essentially custom per user)although if you find a used one it can be sent back to the factory for a check up/upgrades but there is still a time factor.
I would consider this a preferred choice if you have time...and patience....but well worth the wait. List is about $6K new these days (though they may be higher than that now or soon) and I think between $4-$5 used...The main point is though, it will likely be the last pre you will need/want/own, for most people. Well worth the effort but your situation/ MMV...
The other recommendation is the Coincident
Line Stage built by Israel Blume...also in your $5k price range and an excellent performer. Open, transparent stage with just enough tube influence to add the much appreciated "Body" to the performers...There is much written about it on the web...take a look and read.
I'm sure you would find either a good match for your SF power 3's ...Good luck.

Looking to upgrade the pre-amp as the Avalon's are either showing up the pre-amp and or it's just not a good fit (it worked well with my Thiel 6's).

What's problem with the sound? What makes you think problem is pre? Avalon sounds very different than Thiel.

I've had SF Power 3SE+ and SF Line3SE+ (mod to the MAX by PCX) and many more SF pre so VERY familiar with their sound.