Has anyone had any experience with these "Class D" amplifiers yet? I've read conflicting reports, particularly about the XTi1000, which has a very attractive price, and I gotta say, at only 11 pounds, the weight seems quite reasonable. On the one hand, some tests have claimed the amp lacks the ability to reach its stated performance in the low bass region. On the other hand, some reports say that's true only at 4 ohms and that other members of the series do not display this shortcoming.