Damaradona - If you felt that the Cardas cables and power cords didn't make enough difference, I am not sure capacitors will either. I think you need to try different amps instead. This will give you the big change that you seek, especially since you say the sound wasn't thin until you got the VK-60. Just my 2 cents based on what you have said so far. Changing tubes can have a big impact but it won't be as much change as, say, a McIntosh or VAC tube amp would bring.
Arthur
Arthur