Dan, you should first note from the specs that the amp actually delivers "only" a little over 300 watts per channel into 8 ohms. A major factor in the size and weight of a high-powered amp is the need to dissipate heat. Note that the Samson uses bipolar transistors which generate less heat than MOSFETs and that it relies on fans to aid in cooling. A MOSFET amp of similar power which relies on bigger heat sinks for cooling by convection would be significantly heavier and bigger. Ignoring claims about superiority of one type of operation over the other, I'd think that the only factor might be possible noisiness of the cooling fans, although the claim is that the fans are"ultra-quiet"(also note that they offer the fanless Crown amp which makes the lack of noise a prominent point).
