Sun Audio with or without preamp ?

It really depends on how much gain you need, what's your source? Also I used to own those same speakers had them for 6-7 years they sound nice. I ran them with a 17 watt pushpull tube amp and thought it drove them well but on certain, mostly rock, recordings they would seem a tad slow. That was the amp's fault but something to be aware of driving them with a SET amp.

A preamp serves three purposes:
1. Swap between components- which you don’t need
2. Control the volume- which you don’t need
3. Regulate the impedance between the source and the amplifier-

This may interest you assuming you can bypass the volume control. Amps prefer a steady output impedance and when you change volume without using a buffer or gain, which is essentially what a passive preamp does, you shrink the source signal either digitally or using a potentiometer which then changes the output impedance. Passive preamps tend to be simpler and impart less characteristics on the sound. Sometimes this can sound perfectly fine, or it may reduce sound quality at certain volumes. Its really going to depend on how the rest of the system gets along. An active preamp will regulate the output impedance the amp sees which should improve sound quality at all volumes. The downside to an active system is that it adds complication and poor designs may do more harm then good. The good news is you can try out your passive pre setup, and if you don’t like the sound, experiment with an active preamp.