@pcc67
I only listened to my VK-200 as driving the top end of my incredibly difficult to drive Infinity Kappa 8's. Please keep that in mind as I ramble. Currently running Kappa 7's so might get the 200 out again and see whats what.
Impressions:
The VK-200 is different than the 500. It immediately seems more 'live' and immediate. It more forward and has more 'swing' than the 500. I have a feeling since it has less power you can hear the ebb and flow as it works against the speakers. The 200 gets your toes tapping. Initially in the add here for the 200 that I am selling I said something like, "it makes James Brown and Genesis (the band) both 'get up an move' sounding. Sound stage was similar to the 500 but i remember a bit more separation and air, but this might be due to the upper mid and lower highs feeling a bit 'dry' or 'papery'.
The VK-500 is luscious, fleshy, grand, feels more recessed but not less forward (in comparison to the 200). The 500 is a like listening in a larger room. The bass seems to launch the rest of the music into your room or at least is provides a marble foundation upon which everything else plays. Can be scary real. I do not have a typical/standard tube amp in my collection, just a more esoteric David Berning amp, but I imagine the VK-500 get close to that organic inviting tube quality.
Both amps have that startle factor where you get so lost listening that something will happen in the music that will make you jump. Both are perfectly built. The 500 is absurdly heavy--110lbs about. THe lights do subtly dim when you turn it on... The balanced power design of these amps is a godsend! DIrty power is no longer a problem as long as you are using a balanced power conditioner with the rest of your gear.
You could monoblock two 200's? Monoblock 500's is really an endgame setup.