I'm glad to hear that they sounded great with a single-ended amp, but I'm surprised that a 300B could provide the bass power these speakers are capable of. Did you hear the current version? It has a polykevlar woofer instead of the old polyglass. Alan Yun of Silverline says it sounds a bit warmer.
While I am using Analysis Plus speaker cables, my amp is in some ways the opposite of a single ended 300B amp (Spectron II Class D/digital amp with 500 wpc!). However, it sounds very smooth and seductive -- the opposite of what many people expect when they hear about a "digital" amp.
Ken