recommendations for upgrading Bryston BP-26

I'm looking for suggestions to upgrade from a Bryston BP-26 to a USED SOLID-STATE preamp that's as clean, quiet, dynamic and detailed, but "richer" in tonality (if that makes any sense). Kind of like a cross between my upgraded Meitner PA6i and the BP26. My absolute price limit is US$4K.

I have auditioned the Pass Labs X-1 and found it virtually indistinguishable from the BP-26, so that's not an option.

I can buy an Ayre K-1 for just under $3K. There's also a K-1xe with phono for sale, but at just under $6K that's beyond my budget. Also, I'm concerned about the Ayre's relatively high output impedance (300 ohms) and wondering what audible differences there are between the K-1, the K-1x and the K-1xe.

Other than the Ayre, I'm not sure what other viable alternatives might be. Plus the odds are that I won't be able to purchase locally and will therefore not be able to audition--in my system or anyone else's--before buying. It may also be the case that, for the money I have to spend, I can't expect much of an improvement over what I already have: in which case the best thing to do would be to keep saving my money.

Any recommendations appreciated, preferably from listeners who know the BP-26 well.

For context: principle amp is a Son of Ampzilla 2000; speakers, Tannoy System 215 DMT II; digital source: Teac/Esoteric P-70 transport & Bryston BDA-1 DAC; analogue sources: Technics SP-10MKIIP on custom Jean Nantais plinth with Origin Live Silver MKII tonearm and Ortofon 2M Black cartridge; upgraded Meitner FMT tuner; room is 27 x 28 feet with 18 foot ceiling; musical tastes run the gamut except I don't listen to Western classical, heavy metal, or rap/hip-hop.