Based on the reviews and anecdotes I've read, I find the Cambridge S30 rather intriguing--I'll have to listen to it myself one of these days to see (or rather hear) what it's all about. It's extremely impressive that Cambridge was able to achieve such good sound using such a basic crossover, and to get such bass performance out of a small package at this price point--whoever designed those drivers could rightfully pat themselves on the back until they're sore.
That said, it should be noted that with small size comes some limitations. If you like to play music or movies loud, then the bass and maybe even the mid-bass performance of the S30 is not going to hold up. I don't own one, but I just can't see how a small midwoofer can push out loud bass without major excursion capability (except for near the bass reflex tuning frequency), which would be evident in the size and/or shape of the driver's surround (I would think), and the S30 midwoofer's surround looks pretty ordinary. If I'm wrong then let me know, but you can't get around physics.
Then there is the manufacturer's unqualified sensitivity rating of 90 dB, which as an efficiency rating that most people would expect, seems way too high for a small speaker tuned to such a low frequency--in every other speaker I know of, even far more expensive ones, something has to give with these parameters, and in this case it should be efficiency. If the sensitivity were, for example, measured at a single frequency at which the impedance is, say, 4 ohms, and the speaker was measured in quarter-space (i.e. in a corner), then the sensitivity rating could theoretically be inflated by as much as 9 dB total over a 1 watt in full-space (i.e. anechoic) measurement. It's probably not off by that much, but at the same time it's unlikely to be 90 dB by most measures.
Don't take this as a putdown of the S30 by any means--I'm just saying that despite its impressive capabilities, it's still a small speaker in some fundamental respects, and this should be taken into account when comparing it to other speakers (many of which suffer from the inconvenience and ugliness of larger size in order to gain some capabilities of their own).
By the way, it is interesting that the reviewer on Amazon considers the two most objectively accurate speakers of the bunch, the Behringer B2030P and the Ascend CBM-170 SE, both studio monitors (although the CBM was designed for audiophiles and home theater as well), to be "sterile and lifeless" (more than a few people say this about monitors in general, for some reason). I've listened to them both (especially the CBM, as I own a set), and I totally disagree, as they sound very lively to me when the material is, but of course we all hear differently and would form different opinions on top of that anyway. Ultimately, only your own ears can tell you what you like.