Acoustic Reality vs. NuForce

Any opinions on the eAR 501 in comparison to the NuForce ref 9b as far as sonics and reliability? "Thinking" about replacing my BAT VK500.

Front end consists of;

Ayre K3x
Esoteric DV 50 (Modified)
If you are considering the above add to the list the Rowland 201/501's as well as H2o Audio. There are noticable sonic differences in all of them. If you are serious, make certain to audition in home, in your system, with your speakers.

Good luck.
Audiofankj makes a good point. It's always best to listen to amps in your own room with your own speakers. That said, I have heard Nuforce Reference 8Bs against the Rowland 201s and felt the NuForce was definitely superior in midrange and high frequency extension and harmonics. The Rowland 201s were more powerful in the bass and had more power and more slam, but I didn't think they sounded quite right in the midrange and highs.

The latest version of the NuForce Reference 9 seems to have all the bugs worked out of it. It has excellent bass slam and control and the clarity and holographic imaging are strictly top-drawer. I believe NuForce has just extended the warranty on their amps to 3 years and has changed something that makes a "no-load" situation not harmful to the amp.

I've just installed the Benchmark DAC-1 in my system, feeding into the NuForce Reference 9s and the VMPS RM30 speakers and the performance is the best I've heard so far. I'm still in a state of amazement at how uncolored, detailed, and musical my system has become with these latest changes.

But I haven't heard the H20 amps or the eAR 501s, so I can't comment on those comparisons.
Rowland 201 and 501 are ICE-ASP amps fitted with a digital power supply. I think Plato is right on their sound. The H2O uses an ICE-A which requires an add on power supply. The H2O has a whopper of a linear analog power supply. It sounds very different, with excellent mids, and highs on my system.

While I haven't heard the NuForce, eAR 501's, or Rowlands I auditioned and bought an H20 amp which bettered my Audio Research VT100 MKII tube amp. I found that the H20 was more transparent than the VT100, with a smooth upper end, and a magical midrange which is reminiscent of tubes. It is also a very dynamic with with well defined bass. I highly recommend that you add the H20 to your short list of amplifiers to audition. H20 audio has a generous two week audition period so it would be to your benefit to try an H20 amp in your system in addition to the others.