Larry:
I can't find any audio e-zines that have reviewed this unit, but try www.audiorevolution.com click under equipment reviews and you'll see five Sunfire reviews.
Also go to Secrets of Home Theater and High Fidelity(Link Removed), scroll down to the blue bar, click over MASTER INDEX, click over SUBWOOFERS, scroll down until you get to the four Sunfire reviews.
Again, none are of the MK.4, it may be too new.
-Jaime
Larry, I've got a MKII, basically an older version of the MKIV. The performance is nothing less than spectacular. I have yet to find a CD/DVD that this little sub can't handle with ease. As with all equipment, your ears will have to judge the characteristics to make the final decision but it is definitely a sub to audition at the very least.
The Sunfire is a great little speaker, especially if you are concerned about room. I've had my MKII for nearly 4 years now and it has serviced me well. I did have to send it back twice to have repairs on it, although it has been good for the last 2 years.
I do have to admit that it is not as tight, and does not goes as low as other's without some serious distortion. For this reason I am actually selling mine so I can go for a SVS.
If size is important to you, and you do not push your music and movies to reference level, the Sunfire is an excellent choice.