I'm listening to the SPD-4 through my valve setup tonight which is
Radford pre/power amp
Belkin silver interconnects
Usual 1210 setup
Heavily modified celestion ditton 15XR speakers
Nordost SPM Reference speaker cable
OMG!

Its the first time that the celestions have thrown a sound stage wider than the speakers themselves, EVER! The smaller speakers have enabled me to make some sense of the bass, it's even more well defined and taught than the ATC's which leaves me thinking they are reacting with my room and giving me some bass bloom

Vocals are slap bang in the middle of the speakers. This cable just gets better and better. I think there will be even more to be had when I get my celestion 44's set up.