Bryston 28bsst2 worthy upgrade from a krell fpb70?

Hi Lecram,
I have had my Bryston 28B SST2 monos for several years now and I am still very happy with it.
Going by what you already have, the Brystons are a good match with the Maggies and Jadis tubed preamp. Maggies are usually demoed at shows with Bryston amps. The Brystons can sound a wee bit dry, so mating it with the Jadis would balance things out quite nicely. I use a Jeff Rowland preamp which provides a nice touch of warmth to my system.
Of course, if you have any opportunity to bring either the Brystons or another Krell home for an audition before committing, that would be ideal.
Happy listening. J.

I guess we can hear from Lecram whether he would like to mod his old krell amps.

The Bryston 28B SST2 is the one enquired by Lecram, not the first generation 28B. The SST2 version sounds a whole lot different and better.

I agree that the Bryston 28B SST2's input impedance may be challenging to some preamps but specs tell only part of the story. My previous preamp, the Jeff Rowland Capri S2 is spec'd at 80 ohms. While this is more than the 20 times rule for the Brystons, the Capri seems to struggle and the volume setting has to go to almost 80-90% of max to achieve satisfactory levels. When stretched to this point, the Capri begins to sound strained and compressed. That said, my speakers, Vienna Acoustics' The Musik need lots of power to sound good at healthy SPL's. I believe the Maggies need just as much power or even more.
After switching to my current preamp, the Ayre K-5xeMP, which is spec'd at 50 ohms output impedance, I am not sure whether the 30 ohm difference is significant but my ears tell me it indeed is, and very much so. With the Ayre in the chain, music flows effortlessly, dynamics are fabulous with no compression. And I very rarely need to go beyond 50% of max volume setting for everything to sound "just right".
But to reiterate what has been repeated too often, try before you buy, if you can, that is. Sometimes, a home audition with a side-by-side comparison within the context of your own system, may be luxury that is hard to come by.
Cheers! J.

No argument there.
God has spoken.
Amen.

Here's a link that may be of interest :-

ftp://ftp.bryston.com/pub/reviews/Aust_HiFi_July_Bryston_2014.pdf