ALO audio Rx MKII Portable Headphone Amplifier - Black - Reviews
Pros: Build quality, competent performer and good battery life
Cons: Just feels a little low powered and flat sounding
I love Alo Audio as a company and I know they have a strong commitment to excellent products, so it pains me to leave a less than excellent review for them.  Being fair, I have not heard the RX MkIII and I know some of their other products are going to be better than this now discontinued item.
For portable use I tend to have low ohm items:  CIEMs (Frogbeat C4s), Ultrasone Ed. 8, etc.
I bought the RX Mk II as it was meant to pair well with the CLAS -dB and I was using these two with an iPod classic (ALAC files).
The CLAS -dB is outstanding and I think gives my desktop Schiit Bifrost a serious run for its money.  The CLAS costs more, but it is portable and didn't think it could compete with a decent desktop, boy was I wrong.
However, I find, even with the 25ohm Ultrasones that the RXII lacks power.  The sound feels thin, light and lacklustre.  Even on a high gain it just doesn't deliver much force, which I find surprising.
This doubly so as I am not someone who likes my music loud.  However, I do like it with an air of authority, competence and a relaxed power.  The RX does well to amplify the sounds supplied to it by the CLAS in that it makes them louder, but it just feels that something is lost along the way.  I seem to get more volume if I plug directly into my iDevice, but then I get SN issues, jitter and a whole load of stuff best left behind.
When using the -dB and iDevice via the desktop amp (not a fair comparison I agree), an icon audio HP8 Mk2 I am instantly transported into another world effortlessly even at very modest volumes, a low gain setting with the volume at around 10%.
The RX MkII sound is clean and has very good SN ratios to my ears but to be honest, my Fiio seemed to deliver better results (not as good SN but a lot more musicality and power) and cost me a third of the amount.  It's a shame I gave it away to a friend when the RX II arrived in the mail.
It's been about 6 months now and I still am not convinced by it.
Currently I am exploring other options.  I had thought about the RX Mk III but I feel so deflated by the Mk II that I don't want to spend out on something that leaves me feeling like this again.
Perhaps it is the pairing, but I am sure that the variety of low ohm headphones and earphones I use should have allowed the RX Mk II to perform.
No matter what combination of DAC, source, cable, headphones I use with the RX it always comes across as the weak link in the chain.
The other issue with it is simply the control layout relative to the inputs and outputs makes volume control a bit of a pain.
So, ALO didnæt hit my sweet spot on this one, but I'll happily give them another chance in the future.
I might get both a continental and an RSA hornet to compare the two.  I reckon the continental might be a little special, but we'll see.
Pros: For its size packs a sonic punch. Long lasting battery life. At current price point a bargain. The silicon bands are solid.
Cons: Stencil smears off easily and volume control is awkward.
After several weeks of auditioning I feel comfortable sharing my impression of this portable amp.  In comparison to the FiiO 11 it provides more battery life and improved amplification.  I like the expansive sound that it provides out of my Rockbox iPod 5.5G and my MacBook Air.  The signature feels transparent and I did not hear any coloring.  I feel the amp is more than adequate to drive both my HD595 and HE400. It paired well with the DF out of my Mac and the audio out of my iPod Wolfson DAC felt warm and authentic.  At $349 I feel it is a bargain.  At the original $449 it would have been a more marginal call.
At this price I would not expect that the stenciling would smear off.  For portability this amp is fine with a laptop but rather heavy to haul around in a pocket, especially in comparison to the FiiO.  The volume control is awkward in comparison to the FiiO.  The build quality is solid and significantly better than the FiiO.  
Price is the issue for me at $349 I can say that the amp gives you "bang for your buck" but at roughly $60 the FiiO 11 does as well. I would recommend the amp at this price.  The amplification for its size and the battery life it gives you are impressive.  
Since I bought this off the Amazon ALO store I wasn't given the option to buy the wallet, which I now plan to purchase. The stencil smearing may have been less of an issue with the wallet.  The silicon bands which are provided are solid but not designed to prevent smearing..