Best tube preamp for Quicksilver V4 tube mono's (newest KT150 version)

Just purchased a pair of Quicksilver V4 mono tube amps, the newest KT150 version.  Will be arriving this coming Wednesday.

http://quicksilveraudio.com/products/v4/

Single ended
Input impedance is 100 K ohms
Input sensitivity is 1.5 volts

Now need to purchase a nice preamp.  Would like to get the most 'bang for buck' by getting a very nice condition used pre-amp.

On my radar so far is:

EAR 868
Audible Illusions M3b or L3a
Herron VTSP-360

I have had 2 different AI M3a pre-amps in the past, so I am very familiar with Audible Illusions 'sound'... not sure what is the differences between the AI M3b and AI L3a, besides the M3b having  phono stage options and the L3a remote controlled volume?

No experience with Herron or EAR, but from what I have read EAR, if compatible, may be the best performing?

Suggestions greatly appreciated. 

Also would like to hear from other V4 owners.


Rick