What sonic improvements with a high end pre-amp


I've been considering "upgrading" my pre-amp but have been wondering what sonic improvements one might expect with a "higher end" pre-amp. That is, is this the area to upgrade or are other area's going to provide more substantial improvements. For some reference, my current system consists of Merlin VSM speakers, Quicksilver V4 mono amps, Audio Research SP14 pre that has been modified by GNSC, well tempered tt and ack DAC w/audio research CD player used as transport. Basically, I'm curious if upgrading to a dehavilland ultra verve, a supratek, or aesthix...would be a great move or should I look elsewhere. Thanks for any advice that may be forthcoming.
redcarerra
the tube-rolling point is worth emphasizing: if you haven't played around with NOS in both your pre and power, you're missing out on potential huge sound differences. a tech guy once said to me that the sound of tube gear is mostly a factor of the transformers and the tubes you're using...
I, too, have the VSM mm (modified). First, the modification is something you should not hesitate to do.

Recently, I replaced my active linestage with my Placette RVC passive. Oh, my! I have found more dynamics, outstanding soundstage, certainly a tonally and hramonically great sound. Absolute silence with my Atma-sphere amps (MA1s w/upgrades), Hagerman Trumpet phono pre, and vinyl system. Working with ICs and speaker cables was a must, however.

I recognize that many do not go for the sound of passives. All I can say is try it. The RVC can be found on A-gon used for a reasonable price.
IMHO spend the money on room correction or treatment. This will give you the most bang for your buck. This may also identify other problems in the system.