Hello Abe av, I have been shopping for some time for replacements to my Aerial 10T's. I have heard both speakers and I think I am not going to go for either. The S5.4, in my opinion was a step down from the C2s. The C2s had the best imaging and delivery of information I have heard in an under $20k speaker, especially in the mid-range. However, they had a few faults. They had a bass extension in the mid-bass and a lack of bass in the low/mid bass (sounded a little punchy/unrealistic). They also lacked a little "natural" brightness in the upper mid-range, making voices sound a little flat. This dip in the upper midrange i just can't get over. I am going to see if the C4 maybe the answer. If not, maybe the Wilson IIs, Egglestonworks Andra II or Sonus Faber Amanti. Good luck and let me know what you do.
