The Bat 50SE preamp with bat 150SE amps is one of the best combinations i've ever heard. The Atma-Sphere's are quite nice too with the 50SE preamp (I'll assume it is pretty close sonically to your upgraded 5i). I'd buy the bat's if it were my choice. I find that having tube pre and power really brings on the 'tube magic'.
For my tube based system I use vk-5i (w/nos tubes) and a vt100m2 with kt88's. It's a wonderful combination. Not as transparent or dimensional as a bat se combo, but warmer and more full bodied. You might try a vt100m2 or m3 as an additional alternative.
For my tube based system I use vk-5i (w/nos tubes) and a vt100m2 with kt88's. It's a wonderful combination. Not as transparent or dimensional as a bat se combo, but warmer and more full bodied. You might try a vt100m2 or m3 as an additional alternative.