I've found the sound of the Aero to be pleasing both running direct and through my Presence Audio pre-amp. Clearly, system balance and preference will play a role in which route sounds best, but it's nice to have a choice.
Running direct sounds a tad more immediate, lively and engaging, but running through the pre-amp certainly doesn't wreck the sound, and in some ways--richness, air, harmonics, I prefer it. When running direct vs through a preamp the type of amplification one uses is, of course, critical to the sound. I use the solid state Edge amp, so having a minimalist tube-line stage in between the Aero and the amp isn't necessarily a bad thing. Now, if I were using the Tenors or other high-quality tube amps, well, that might be a whole 'nuther ballgame. :)
As Sos said, it really is about system balance and tuning the system to its most pleasing state--and that is to a large degree, different for everyone.