System edited: Based on the very helpful responses I swapped my speakers (and their cables) and am very pleased with the result. I am happy now, but may look at the electronics in the future.
Thank you to everyone for the extremely helpful recommendations. I ditched the cables and replaced with 10 AWG Belkin cables that I terminated using Canare locking bananas. At the same time I changed to PSB Stratus Gold speakers. The sound is a lot more of what I am looking for. They are more articulate with a bigger soundstage. Happily I did away with the wooden blocks as well. I had put the Vandersteens up to raise the tweeters. My next upgrade will either be to the cd player or to the amp.
I appreciate all the advice. I know there are a number of compromises in the system, but I suspect that particularly for the sound I seek the speakers are the biggest problem. They sound sweet and warm but I am looking for something with a more clinical sound.
Perhaps I am being unrealistic, but my point of comparison is my Sennheiser 595's playing through my Headroom Airhead. With the headphones there is a crispness and detail that my hifi doesn't come close to. I don't expect to have a headphone sound, but I would like to get increased depth. With respect to my system, I think that each component has substantial compromise built in. The preamp is famous for clarity but at the expense of low end. The power amp is flaky in the high end. Most significantly the speakers are have a full sound but with a notable hole in the midrange. I think that my next step will be to change the speakers and exchange the 13 guage speaker cable to 10 guage. After that I think it would be good to get a bit more power - the Roksan delivers 70 wpc @ 8 ohms.
