With all due respect, Trevorsplace, if you were unable to blend the subwoofer with your mains, you obviously did not due a thorough job of setting the subwoofer up. ALL subs are highly dependent on placement; Sunfire subs being even more sensitive to placement than some others from my own experience. I've got a MK IV, aka the 11" cube one, and get anywhere from almost no output to stucco cracking output depending on where I place it with respect to the walls. If it sounds boomy, your placement was 100% to blame. My sub sounds tight with music and raises all kinds of hell with movies
Don't belittle a sub just because you did not properly set it up and/or find good placement.
Now, on to less confrontational chat, I'm currently looking to up-trade my MK IV for a signature for the additional 6dB output. (more is always better right?) Assuming my local dealer doesn't jerk me around (they shouldn't, I've dropped about $6K there the last 6 months alone) I'll have the signature early next year and I'll then be able to give a straight-up no BS answer about how it performs. The whole line of Sunfire subs uses extremely long-throw woofers, on the order of 4-5x the excursion of other drivers. SPL for a subwoofer is dependent on how much air a sub can move. Well, my sub has 8" driver, but about 2.35" of excursion. Translation, it moves as much air as several less exotic 15" drivers. These subs also use a monster digital amp to deliver loads of power. They may be rated for 2.7KW, but usually are only delivering about 250-350W, with an average of 600W at max SPL. This is due to the way the sub and amp are designed and the amp being able to swing +/-105Vrms to combat the high back EMF from the huge magnets on the active driver (225oz magnet on my MK IV, probably bigger on the Signature). Read the whitepaper if you'd like to know more, or even look up the patent; I did, it is really interesting reading.
Take any in-store listening with a grain of salt. When I was looking for my sub, I was pretty close to sold on it just from the specs, but I needed to listen. I walked into one of the local dealers and gave it a listen. I was so upset by how poorly it sounded, I almost didn't buy it. However, I took the MK IV home and just set it in a corner in a rather happenstance manner. I hooked it up, turned everything back on and was greeted by some really loud and loose bass. Boomy as all hell; kind of what Trevorsplace above reported. Well, I took some time, adjusted the placement, and now have very nice and tight bass for music and some major thump for watching movies. Placement is everything; moving the sub as much as a few inches in any given direction can change the sound from boomy and loose to tight and musical. It is all about placement.
Don't misinterpret what I am saying about these subs, they are
NOT for everybody. There are less expensive, though much larger, subs that will beat the Sunfire subs; nobody questions the amount of ass SVS kicks, but they are not for everyone. Sunfire subs are not for everyone either. If you don't want to fiddle with placement a little, save yourself some time and don't look at the Sunfire subs. If you have some patience, you will be rewarded with crazy SPL, tight bass, and only 13" cube, assuming you get the signature, whereas any other sub will take up quite a bit more space for the same kinds of output.
Sorny