Spendor SA1 - Quite an unassuming sound, pretty neutral, nicely detailed, not greatly extended bass due to its small sealed cabinet, but quite a natural, even bass, if a little light compared to the rest of the group.
B&W PM1 - Beautifully open treble and amazingly detailed. Quite a lot of bass for such a small standmount with a small bass driver, but like all mini monitors, you're not going to get gig levels with bass heavy material. Lovely build and finish. They like a bit of space to work well in, despite being front ported.
PMC DB1 - One of the lighter (weight) models here, so it may not feel in the same quality as the likes f the LS50 or PM1. One of the livelier performers of the group that still sounds exciting at lower volumes. Can sound a little boxy in comparison to others in the group.
Kef LS50 - More akin to listening to headphones with their ability to stop/start. Great detail and projection. Bass isn't the deepest here, but what they do have is pretty solid. Like the PM1's, they do like a little bit of space to stretch their legs.
Acoustic Energy AE1 MKIII - I have heard the MkIII's but it was quite a while ago, so it would be unfair of me to comment. I did hear the Classic version more recently.
ATC SCM11 - Sounds a little restrained in the top end compared to some of the other models here, but they posses the largest bass driver of the group and would probably win out on SPL. Again, pretty neutral, with a nice even bass due to a sealed cabinet.
All of these models need capable amplification to get the best from them, the level of which varies depending on the model. The PM1's, LS50's, and DB1's have greater presence than the other speakers, which tend to lack a little in comparison at lower volumes.