Advice on a preamp

If you can find one used, a TRL DUDE tube preamp will give you powerful, defined bass with the rest of the range beautiful with great clarity and a large, deep soundstage and tremendous dynamics everywhere.  The unit is large as in 75 lbs. but the sound is all you could ever want.  Used price will be about $3200-3800 depending on the amount of extras and custom parts.  All of the DUDES are very fine sounding.

It's a bit above your budget, but if you can stretch a little, it might be interesting to try a Herron VTSP-3A in that system.  I haven't heard anything better. 

Used Aesthetix Calypso Signature, if you can find one.  I started with the Calypso, mistakenly strayed... found a used Calypso Signature about 3 years ago and have no intentions of trying anything different.

Any one knows how much does it cost to upgrade from Calypso to Calypso Signature.  From what I read, Aesthetix provided such a service.

No one suggested a McIntosh or an Audio Research preamp. Is that because of the price or incompatibility? Just curious.