After 2 days of listening I observe the VK-75se has more "space" around each instrument; a bigger, way more open stage; better dynamics. Treble is brighter, but not etched. Everything has more substance - like turning the saturation up on a digital photo, but not as much as I expected it to be. It definitely has less of the "tube sound" than I expected.
VK-75se has unbelievable bass. I've unhooked the subwoofer and don't intend to put it back in the system. Bass is very substantial in Trittico/Pomp&Pipes, EnVogue, 1812 Overture (cannons), Steely Dan. Gotta go back and listen to VK-500 to confirm this as it just doesn't make sense.
VK-75se plays very loud. With 4 ohm Piega P-10s hooked to the 4/6 ohm taps, I get 100+ dB with the volume knob at 55 (vk-5i, vk-d5se).
On the other hand, it is physically even larger than the VK-500 (deeper), and weighs just about as much. The pictures don't convey its true size (2' deep plus cables). I can't describe this well, but I think the bass is punchy, but a bit "rounded" (is that mutually exclusive?). I notice on some R&R the pace seems to drag, e.g. Heart "Magic Man," but not so much in the classical/jazz stuff.
Wife recommendation is to keep it, as she likes it better too.
