Alot depends on your associated equipment (besides just the amp). It's commonplace to match speakers with amps and amps to preamps. However, whenever you change a component like the preamp, the entire setup must be thoroughly considered.
Almost every preamp (outside a good passive) adds a distinct flavor to the sound. This "flavor" needs to be considered when mating to your other components.
For a simplified example... With certain laid back speakers, the ARC LS25 may lack some of the bass impact and transparency that would complement these types of speakers. On more "up-front/agressive" speakers, these traits may work perfectly.
On the flip side, many of the new ARC models like the LS-25 sound less tube-like than other tube designs. If your setup could use more/less midrange sweetness and tube-like attributes, then those factors will need to be considered in choosing the appropriate preamp.
Unfortunately, unless someone shares your same system and tastes, you should weight the suggestions you get accordingly. Nevertheless, I will point out one thing with the LS25. It's very expensive and alot of the cost is due to having a complete set of balanced AND single-ended connections on the back. If you don't need this flexibility, then you may consider other options from strictly a value proposition.
