Nick,
I'll try to be objective...
I absolutely love the Blue Circle CS Integrated! :-) As you say, it's "a little guy", but I like to think of it like you'd see a cute little kid with some serious talent. Certainly it is not on par with decent separates, but for $1150 I do think you get great value for the performance it does deliver.
Best way for me to describe the sound is to quote two of my customers. The first bought one to replace a Manley Stingray that he had to sell; he said "it's close, really close. At half the price, there's no question I prefer the CS integrated." The other customer's first reaction to it was "there's no tube? Really?" So basically I'd describe the sound as warm, engaging, with a tube-like quality (I personally won't go as far as to say it sounds like a tube amp, but it is night/day from most analytical sounding solid state stuff).
As far as the power goes (and whether it can run the Focus FS688), I use this integrated with a pair of FS688's in my office. My office is relatively small (12ft x 14ft). Honestly, if I was using it in a bigger room that was more for listening (and less for work), I'd feel that I'd want just a bit more power than the CS Integrated delivers. If you try to push the speakers with it, you notice that the bass loses a little bit of control. In a smaller room at up to moderate listening levels, I think the BC integrated does a very nice job with the FS688 (the FS688 has a relatively flat impedence curve, so even though it has a relatively low sensitivity of 85db, they aren't tremendously hard to drive). It may be a tougher sell to drive the FC-70 (which is 4ohm and needs a good high current amp).
I'll say unequivacally that the FS688 deserves *far* better electronics than the CS Integrated. This is not a knock on the CS Integrated, but the CS Integrated is an entry-level product, and the FS688 is in a performance class far above.
I've never heard your Linn Pretek or Bryston 3B, but I have heard a later-model Bryston 4SST (?). Sonically, I think Blue Circle overall is much more engaging when comparing comparably-priced amps. Bryston, paired with the right preamp, can sound very good, tho (maybe a Blue Circle preamp? Hmmm.. ;-)).
Hope this helps!
Phil
Sonic Spirits Inc.
www.sonicspirits.com