Adding my 2-cents even though you have your Tone Beast. I had one of those and from my perspective, it's well built, great sounding and very versatile. Customer support is top shelf.
I also really like the Neve 511 for the high value / sound quality / price point. Using
Front End Audio's Rack Attack option, one can get a Neve 511 bundled with a Fredenstien Bento 2 for $684. Still a lot of money for a single channel preamp, but wow - end of preamp search for me. + 1 @ Jim / Neve products. I've never enjoyed my microphones more either. No buyer remorse - none. I may get another one since I have an empty 500 slot staring at me. I need it, I know I need it... :)
One more thought, the ISA One as AT mentioned is another post I can +1 from owning one. They can be found used for a decent price. Plus you can use the ISA One for a really good DI and a Mic Pre at the same time. But I see you had the ISA Two, so you know what they sound like. FWIW, I'm keeping mine unless I give in to the want of another 511.
All the best and enjoy the Beast!