These two sound very different. The Aesthetix is brighter and airier and tipped from the lower midrange up in balance, with a little better soundstage depth. The BAT will be a little darker and have a fuller, bigger, more fleshed out sound, with some of the best bass out there but not as resolving up top. The BAT is MUCH quieter than the Aesthetix. I had both here for close to a month and sent the Aesthetix (calypso) back and kept the 31SE.
This is not to say the Aesthetix is bright or the BAT dark, just in comparison to each other.