I have a friend who uses the PowerPac 120's to drive his rear surround speakers, and he's very pleased with them. The "120" version is simply one channel of amplification taken directly from the Bryston 3B-ST, which is their 120 wpc power amp. I do not have first-hand experience with the PowerPac 250, but given its power rating it is likely to be one channel of amplification taken from the 4B-ST (250 wpc amp). I own the 4B-ST amp (as well as a 5B-ST, and Bryston's SP-1 pre/pro), and recommend their products highly. You may be able to obtain more info about the PowerPac's from Bryston's Web site at: www.bryston.ca. From their Web site, you can also send an E-mail to James Tanner with any technical questions you have. James is a great source of information, and always responds very promptly to inquiries.