You know what, I took some more time to look over your setup and it's not bad. I apologize for not checking more carefully before. If you're still looking for upgrade paths, I'd focus on the DAC next. If you want a smoother, warmer, more expansive sound, you can look into an M^3+Sigma-11 amp. If you want to keep the same sound but upgrade "technically", then look into a used GS-1 (esp DACT). Alternatively, for a more subtle upgrade, you could pick up a used aftermarket cable. My favourite is the one I'm using now, as it's the only silver that has retained all of silver's inherent benefits without the thin, wiry sound. However, if you're looking for something cheap, get any UPOCC copper cable. I've seen some go for as low as $100 on the sale forums.
skeptic posted some good recommendations, but I'd remove the Sheer Audio stuff form his list. I owned their best offering. It was nothing like the Headamp products, despite being based on somewhat similar Dynalo designs.
