Either you need a HP amp, or you don't. If you don't hear an improvement with the L30 II, and don't need the extra clean power for more volume in your phones, then you don't need an extra HP amp. The L50 sounds exactly like the L30 II, and these are some of the most clean/transparent/powerful HP amps available. With the L50, you'll have a better, pro audio connection with balanced TRS cables and passthrough for your speakers, but that's about all you'll notice. A different/better DAC may improve things a tiny bit, but I'm not sure you'd even notice the difference with a different DAC. You also have to take your headphones into account. Depending on how they synergise with your dac & amp, and how much detail your ears are able to extract from them, this also makes a difference. I have Arya Stealth's but I never use them for music production or critical listening (I rarely use them at all, actually). However, I do know that my Stealths sound better to me when I use them with a Ifi Zen Can amp (as opposed to a L30/L50) and that's because that amp has a bit of crosstalk & distortion that makes the headphones more pleasant to listen to, and here at ASR, crosstalk & distortion in an amp could be considered lousy performance. Maybe different headphones is what you need. It really does depend on what you are trying to achieve.
