I guess I wasn't too clear about what I meant in my post. The op had stated he was looking for efficient speakers which implied he was concerned that the Cronus's wattage wouldn't be adequate for inefficient speakers. This is not the case. 50 tube watts will Krank! As for the differences between the standard and Magnum Cronus, I would expect that sort of difference you describe with any speaker regardless of efficiency. The upgraded parts, power supply, tubes and, to a lesser extent, wattage of the Magnum should sound more dynamic than the standard. It wouldn't be worth the upgrade money if it didn't sound better. But I think that improvement had nothing to do with the efficiency of your speakers. Sorry I wasn't clearer before.