There actually is a decent short review of the SRM-007A on InnerFidelity driving the 009. Bottom line, sounds decent at moderate levels but loses it at higher levels. If you are willing to do some DIY there is a relatively inexpensive fix, which consists of replacing the output plate resistors with a constant current load. Same fix applies to the T1/006 series, which is less expensive to begin with. It does void your warranty, though.