Just bought a pair of Grado GS1000i, considering a new headphone amplifier.

Hello!

Let me begin by thanking for a great forum.

Anyway, I recently bought myself a pair of Grado GS1000i. I already had a pair of AKG 701 and a Lehmann Audio Rhinelander headphone amplifier. Must first say that I first was not particularly impressed by the Grado headphones, but after some burn-in (around 50 hours), the headphones are a bit better in all aspects, which they should be given the price difference. But I have heard that they may need up to 200 hours to sound their best.

Now for my question. Is the amplifier Rhinelander sufficient or should I upgrade? I'm thinking of Lehmann Audio Linear or Naim Headline with NAPSC. I've heard from some that the difference is small between the amplifiers from Lehmannn while others say the opposite. 

I do not want the amp to be a weak link in the system. Though this may not be the case?

I have a Rega P5 with external PSU and a Music Streamer II + (2011 version) as sources.

Thank you