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.

Your Sanders Magtech Amp has 100kohm input impedance, a perfect candidate for a passive preamp.

So the specs on Sanders' site are incorrect for the Magtech.  According to an email from Roger, these are the correct specs:

"I designed the Magtech using a FET input stage so that it has a very high input impedance (100K) when used in single-ended mode. When used in balanced mode, its input impedance is only 1K, which is too low for many tube preamps."

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

According to an email from Glenn back in June of ’16. It’s usually $2500 to upgrade from a Standard to Signature, but I think it depends on when the Standard was made. It’s $3500 to go from Signature to Eclipse and $5500 to go from Standard to Eclipse.

I thought about being the guinea pig for the Calypso Eclipse but decided just to get an ARC Ref5SE instead.

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

I just got an ARC Ref5SE this week and am running it with a Sanders Magtech. My initial impressions are that it's quite a step up from my Aesthetix Calypso Signature (weightier and purer sounding), but I'll need to do further testing.