active or passive preamp for active speakers

While for my taste a passive like the Lightspeed Attenuator (I have tried many others) is better than any active, as Al says it has to be in the right system. It seems that you system may not be ideal, not only because of cable lenghts, but I suspect the SS amp in your speakers are low input impedance. I also think that passives work better with tube amps in general in terms of impedance and sonic character. As you point out, you will certainly have more flexibility using an active preamp - with you current equipment and down the road.