Although I am going back to Solid State for multichannel setup, I had good services with Sonic Frontiers Line 3 and 1. They are very natural. Since they don't have their own signature sound of their own, you can add your flavors with different tubes such as Amprex 7308 NOS, etc.
BAT VK preamps are nice also.
BTW, both Line 3 and 1 are for sale. Any interested parties?