Preamp-power amp interconnectors advice

Prophos: If you're not willing to take the positive suggestions and advice as well as a very different viewpoint here than yours, you're on the wrong site.
Your priorities are indeed your own. But to claim dynamics and bottom-octave bass and any kind of reasonable soundstage attributes with a cassette source is silly at best relative to LP and digital sources. Chasing cables and noting capacitance in this implementation is futile. $100 cables will be so compromised and not any less so than $20 cables.

Hope it all works out for you.

I think he is listening, but we just threw too much of an authority at the man, and naturally he doesn't like it. Who would?

Inna: You are right. He's heard enough criticism. Now he's on his own.

If you're planning on upgrading the amp and/or preamp anytime soon I'd personally skip this step and focus on getting the components right. However, if that's not going to happen for a while and you're just looking to find a way to live happier with this setup you might stretch your budget a bit and try the Acoustic Zen Matrix Reference. The original version (i.e. not the Reference II) would probably work best since they're quite a bit more laid back in the treble and richer and fuller in the mids and bass. And they're probably a little cheaper than the Matrix Reference II if you can find them. Looks like they can be had for $250 - $300 used, and if they don't work you can probably sell them fairly easily for little or no loss. Best of luck.