I'm using a Hafler TransNova 9505, which provides a very fast and accurate bass with my transmission-line woofers(actively bi-amped). If you are looking for a lower-budget/high-slam factor: Look at the "Best amp for the cost of dirt" thread in here(same forum). A number of people are using the Behringer A500 full range. It should make a good subwoofer amp. Hard to beat for $200.00 to your door. (http://www.samedaymusic.com/product--BEHA500)