The LS 500 and another Energy model are very similar at Audio Advisor. I think AA only has the LS300 floorstander now. Athena was doing pretty well and all of a sudden they fell off the map. I believe the ones you are talking about has the 2 8" woofers? They are very efficient and have great power. You will need a pretty food sized room for them too. They are not bright but can be boomy if you don't have the space. This model replaced the Model 2 and are similar to the Athena 2's that Stereophile had on their reccomended list a couple years ago. With the right amp they can sound mightly inviting. I personally think you should get a hybrid amp like the Pathos or other that have great midranges and a smooth and extended top end. Also an amp that can control the bottom end. I think they are great in a Home Theater setup in a medium to small room. The 8" woofers move alot of air. The parts quality is pretty sub par. I can only imagine how this speaker will sound with better crossover parts? They throw a big sound stage and are pretty good sounding.
The Monitor Audio will be a very different sound. It will not have the amount of bass the Athena has and the top end of the MA RS6's will be more extended and maybe refined. The midrange will be very good and I think better than the Athena 2 with the 2 8" woofers. Some people call that bright. So you must match the amp with them to prevent the brightness. You may need a subwoofer with the Monitor Audio's. Typical British character. But not as refined as Spendor, etc.
The Monitor Audio will be a very different sound. It will not have the amount of bass the Athena has and the top end of the MA RS6's will be more extended and maybe refined. The midrange will be very good and I think better than the Athena 2 with the 2 8" woofers. Some people call that bright. So you must match the amp with them to prevent the brightness. You may need a subwoofer with the Monitor Audio's. Typical British character. But not as refined as Spendor, etc.