Suitable tube preamp for pass labs x250

I used a Cary SLP-05 with my Pass Labs X350.5 Amp and the combo was not good.
There was limted frequencey on the ends and low dynamics.

Suggest going to a Pass Labs Preamp.

Used all of these preamps on my X150.

In order of what I think worked best - all preamps worked well.

1. Supratek Chardonney (more tubey sounding warmer deeper bass) no longer made though.
2. Modwright SWL9.0 (better soundstage more focused sound more prominent treble though not bright, clean , but not tubey sounding)
3. Belles 28A (best tightest bass most extended, great soundstage, harmonically a little thin, great remote control)
4. Joule LA100mkIII - (warmest of all above and not as refined though this is Joules older preamp the newer LA150 , is supposed to sound similiar to Modwright)

Given that you have the X250 and not the X250.5 which is suppose to be warmer, I'd go with a warmer fuller sounding preamp. I'd check out the Modwright (even the 36.5) with tube rectfication (though it is not a tubey sounding preamp it is not thin). A newer Joule the Cary 05 is suppose to be tremendous. Abe Collins used it with his X150 and he loved that combo.

Tvad, the output impedance of the MP-1 is closer to 30 ohms, not 350. Its bandwidth is unaffected by load.