Advice on a preamp

I have an Aesthetix Calypso Signature with the Sanders Magtech running Magnepan 3.7i's.  It sounds pretty good.  I was upgrading from an Odyssey Candela.  It definitely yielded some gains.

I liked the Aesthetix Calypso very much. It is easy to roll different tubes as well.

Happy Listening!

" Great question. A cleaner more detailed sound, better bass control, more refined treble and improved soundstage. An all around more 'live' or natural sound. I did originally have an Opera 100w tube amp but felt it was lacking in power and a bit too warm."

That's some good info. I would demo an Ayre K-5 for SS, and for tubes I'll be the 3rd to recommend the Calipso. You can't go wrong with either. 

Your amps are fine.  Unless you're not happy with them for some reason, I would keep them.

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.