Mantana,
Every encounter I've had with Blue Circle products has been a very pleasant one. Sure, the layout may not look as neat and tidy as other manufacturers gear, however, Gilbert goes to great lengths to ensure parts inside are matched within strict tolerances and often ties it all together using a painstakingly long point-to-point wiring process. Though he has begun to use circuit boards on the output section of his more affordable components, such as the 145wpc 'Katlas' you refer to.
The Blue Circle amp I heard with the Spires is the now discontinued NSCS (great amp!). Because I did not drag the MA7000 with me for a direct A/B comparison, it would be unfair for me to try and arrive to any final conclusions as to how the two compare.
That said, I feel comfortable enough to state the obvious differences between the two. First, both products are well built and should last a long time. Both have lots of power, though the MA7000's additional bandwidth gives it the advantage when it comes to handling extremely dynamic passages. The MA7000 also possess more clarity across the board and is in general more linear sounding in the hi-fi sense of contributing very little flavor to any particular frequency band. It's very much a "tell it like it is" piece, which is a sharp contrast to the MA6300, MA6500, and MA6900 integrates. What the MA7000 gives my Vantage's is a greater sense of sound-stage depth and refinement. I'd expect the same to hold true with the Spires.
The Blue Circle integrate by contrast had a touch of warmth in the mids that really worked well with the Spire's. Though well extended in the top end, the Blue Circles had an extra sense of 'grit' in the treble which in my opinion, helped to give instruments a more authentic tone. Some may prefer the MA7000's smoother treble though. Overall, the Blue Circle NSCS is the more colored piece. It's sound has rougher treble, a more blossomed midrange, and great textured bass that never calls attention to itself. Still, it doesn't sound as refined and as balanced as the MA7000. Of course, given the price differences between the two pieces, this isn't much of a surprise.
If someone were to approach me about what amp I'd go for, I'd vote for the MA7000 in most circumstances. I love its autoformers, its linearity, bullet-proof circuitry, and the company itself. Of course, its up to each person to decide for themselves whether or not its worth the extra money to go for a piece like the MA7000 when considering such great affordable products from the likes of Blue Circle Audio. If you want to stay within the McIntosh line, a great alternative would be the MA6600. It's only moderately behind the MA7000 in performance, is $2000 less, and can even have a tuner added to it, making it arguably one of the worlds best stereo receivers!
Anyways bud, there are plenty of excellent integrate's out there for your Spire's. Good luck in the hunt!
