In which amp was this? My friend has tried EML solid plate 300B, "current" production WE300B (as I understand WE isn't currently making the 300B) and old stock WE 300B. In his amp the "current" WE 300B sounded best. His amp is also incredibly transparent as far as 300B amps go.
For really bargain basement you could probably pick up an EMU0404 usb for around $150. I'm not sure if it's truly balanced or using some opamp shenanigans.
I am interested in measurements of the ESP950 on the KGSS vs E90. To see if there is a measurable difference. Don't worry I'm not doubting the KGSS sounds much better