Just curious, purrin, what volume do you measure at? I'm not sure if it's a product of the Burson HA160D amp or the LCD2 R2s but when going to VERY high volumes, the upper mids become intollerable, and it spikes quickly. I'm almost wondering if this is the resonance at 5k even more pronounced at high volumes. Then again, could be the Burson as well, but something gets out of control pretty quickly past a certain volume (thankfully a very high one).
Doubt it's the Burson, I never noticed that from it before. Never noticed the spike either w/ the two r2s I liked and I'm really sensitive to spikes around 5k. Not sure if it's your phones or some source issue w/ your synergy.