If you still have that M500, the VTB-1 ought to complement it well.
When Harvey Gerst reviewed the VTB-1, it went great with a RCA 77 ribbon.
The VTB-1 is a "sleeper" mic pre-underated IMHO.
It's a bit on the dark side, so it goes well with otherwise bright LDC's, ribbons, and those (like me)...