Tube Amp & Preamp for ML Summits?

Not exactly on point, but some suggestions that I have tried and like with the summits (but slightly over your budget):

Parasound JC-1's with Blue circle bc3000 mkII pre
Parasound JC-1's with CJ CT-5
Blue Circle 206 with Blue Circle bc3000 mkii
Blue Circle 204 with Blue Circle bc3000 mkii

The BC pre has a remote option, I do not have it on mine. The CJ has a remote. Both the BC 204 and 206 are hybrid amps. The JC-1's are ss but sound pretty sweet with the summits.

All were using APL modified Denon 3910 with Redbook.

Given the budget, I like the JC-1's for the summits, althouth not tube. You might try another CJ amp or one of the other tube Pre's out there in the 2k+ price range. You might try the Modwright or the Supratek Chardonay. Good luck.

I have not heard the Summits but am familiar the Martin Logan sound.
Summits have a powered sub. They xover @270hz.
You are in a biamped situation. You are using CD which has a higher output than phono. This means you can go for nuance over raw power.
I was just reading a review of the ASR Emitter on Audiogon which is available in Europe for a reasonable price.An integrated is a serious consideration. IMO preamp or linestage is not necessary for CD. You might also try the Rowland Research integrated. You might want to try some tube integrateds also.
My GNS modified ARC-SP14 and Moscode 401hr comes in at $7k which you might also want to consider. Mine is very neutral while others prefer a sweeter sound.

I talked to VTL about a ST-150. They stated they have tried that amp with the Summits and recomended something with more power. Unfortunatly the Summits dip to 0.7 ohms at times.