I never heard an actual C7 but I built one from the schematic a long time ago. As I recall, it sounded very nice, just lacking a bit in dynamics. From looking at your system, I think you would appreciate the improved sound quality that V-Cap coupling caps should provide. Richard is absolutely right that cap upgrades can be risky. They will change the sound, and sometimes a modern cap can be a step backwards. I happen to like the sound of V-Caps very much, both the original Teflon and the newer CuTF series, but that is not a universal reaction. I suspect your C7 uses some mylar film caps from the late 1970s, and V-Caps should be a major improvement in inner detail and (probably but less certainly) tonal balance. If I were you, I would do it. In the unlikely case that you are not happy, you can always put the originals back in.
By the way, if you need a copy of the schematic, send me an email through the Audiogon system. I have one in my files somewhere. As I recall, it shows the original circuit as well as later updates.
By the way, if you need a copy of the schematic, send me an email through the Audiogon system. I have one in my files somewhere. As I recall, it shows the original circuit as well as later updates.