Move your speakers further out into the room. Even an additional foot can reap large sonic rewards. You should also experiment with sitting closer to the speakers.
Definitely go all balanced.
In this
review from Soundstage the writer notes that Vienna Acoustic demoed your speaker with the Ayre integrated, but he thinks they responded quite well to higher powered amps.
Definitely do something about the the wall of windows...curtains, blinds, etc.
Upgraded audio software could help.
Do the above before changing you D/A or computer. Whatever you do, the last think you need is a subwoofer. Your speakers put out more than enough low frequencies for the music you mention and your square room will make deeper/louder bass more of a problem than a solution.
Please post what you do and your impressions.