Need fast help picking preamp before its too late

Sorry to introduce a wild card, but the Klyne SK-5A here at $695 is IMHO a whole other level of machine, a clear winner if you also have vinyl. ( Its phono stage is super. ) I guess it may be out of your price range, but it preserved the detail of my Shanling CD-T100 and it would do the same with the Music Hall you have.

If you haven't had a tubed pre in your system before, it's kind of hard to tell whether you'd like one or not--some don't, many do. I say go for it. Worst case scenerio is that you don't like it and have to sell it at little or even no loss. When I added a tubed pre to my system (CJ 10al), I did so because I wanted to enhance my analog gear, but it was my cdp that benefitted the most. The CJ made my cdp sound like analog--a good thing. Have fun and enjoy.

Have you given any thought to a B&K PT-3? I believe they have been replaced by the PT-5. You should be able to get a new one for around $450 or less? (Retail $595) Another thought. Different spks! I've owned three JM Labs spks.(Chorus 705/707/and an older two-way floorstander, can't recall model # @ the moment, and I've found them to be somewhat bright sounding w/the exception of the Chorus 705. I understand what you're aiming for. Considering your amp, which I've heard others say is warm sounding, MLD is my choice. (Added benefit: Use as headphone amp in the future.)
All good choices however. Good Luck!

I'm not familiar with your speakers. That said, and limitied to your short list, I'd pick the Forte. BTW, a Forte 4 amp would be a real nice upgrade from the B&K ST-140, down the road.

I would recommend your "tube" route first or possibly the Forte.The PS and Mccormick are going to be a little dry.The PS 5.5 was interesting ,but in the end-very solidstate.The CJs are very musical,but not the last word in low,low-level detail.This being said,it won't be a problem until you have invested considerably more on your system.