Switch preamp?

I am going to second Scott_w's recommendation for a Sanders Sound Magtech amp.  It's especially made for electrostatic speakers like the 13a's.  I have been using one with my Martin Logan Montis speakers and the combination is a true dream!  I have tried amps that are thousands more from my local dealer and only have to send them back, because none could touch the Sanders Sound.  The Magtech has been an Absolute Sound best buy for many years.  Mr. Sanders builds them in CO and has a generous 30 day trial period.  At $5500, it is truly a best buy and likely the last power amp you will ever buy.  

For preamps, there are more options I feel.  I personally use a Classe Sigma SSP processor since I also need home theater duty in the same room.  It works great for my needs.  But eventually, once I move to a larger house with a dedicated hifi listening room, I will likely get a true two channel preamp.  Top contenders are ModWright LS 100 ($3750), PS Audio BHK Signature preamp ($5999) or if I am on a tighter budget a Backert Labs Rhumba 1.1 ($2250 on clearance).  I've listened to the Backert and ModWright at HiFi audio shows, so I know they are good.  The common thing among all of these is that they have tubes in the output stage.  I think a tube preamp like these marry well with the solid state Sanders Sound Magtech.

Kind regards and best of luck,
Jason

Jason, thank you. At the end of the day I couldn't part with my Krell KSA 250s. I spoke with Krell tech support and they said due to its age recapping is a must; +/- $1,000 plus shipping. At the end of the day it should sound far superior after 25 years of degradation. Then, based on Artemus suggestion, I started a dialogue with Don Sachs. He knows his stuff and I felt I was in good hands. Because of my age this will probably be my last chance -- I've said this with each upgrade -- to get it right and consequently ordered the best he has to offer for my system. So, some time within 3 months I should have a Don Sachs tube preamp (it's well worth checking his Web site) feeding a rebuilt Krell powering ML 13a. A lot of angst, a lot of reading.... we'll hear.

If you enjoy the sound of the Krell (great product), then a recap is going to bring the life back!  Getting over 25 years out of something is an awesome feat and shows the value you have received from such a product!  

Looking forward to your thoughts on the Don Sacks pre.  I'm always open for good recommendations.  

In the end, it's your ears and no one can argue with that.  :-)  

To my ears the best combination with my Martin Logans was Cary tube preamp with pwerful class A solid state power amps.  I tried several different power amps matched well in this scenario

Well, I finally have my Don Sachs preamp along with an entirely new system. What started as simply replacing KEF, Polk bridged speakers with Martin Logan 13a ended in a completely new system comprised of the Sachs preamp, PS Audio’s DAC and CD player and Krell 575 monoblocks (while I was getting my Krell KSA 250s recapped, I received a trade-in promotion e-mail that resulted in the monoblocks).

It should not go without saying that what was a stressful endevour was made palatable by the fine people at Krell, PS Audio and Don Sachs. If I was ever to jump back on the merry-go-round, which I won’t, I’d undoubtedly go back to the mentioned companies due to their service being above reproach. Fine people.

Humbly, my system is fantastic. In good measure I have the Audiogoners who recommended Sachs to thank. It was well worth the 4 month wait. The preamp far exceeded my expectations.

After 50 years my rabbit hole is filled, well, almost, there’s still some interconnects and power cords to consider...