I met the Rhapsodio folks for coffee today --- quite an interesting conversation. I can't really comment much, as I didn't bring my own music, and we were talking most of the time, but I thought the RDB+ 2V1 was quite nice --- quite similar to how AnakChan
put it, "neutral-ish" IIRC. The R-1L was similar to the ER4P, and I didn't use any of the amps, so no listening impressions. However, I was very impressed with the build quality of the Shozy PX-M1. It's as good as any on the market, and definitely some of the best build quality to come out of China, bar none. Unfortunately, the PX-1 (not the PX-M1) has a bit of an egregious spelling mistake; they call it a "Headphone Aplifier" LOL. Luckily, the PX-M1 doesn't have the same problem. However, if you're considering the PX-1, I'd wait until they get their Engrish fixed.
Some Pictures:
RDB+ 2V1
R-1L
Shozy PX-M1, PX-1, Panda P&D AMP-K PRO
Shozy PX-M1, PX-1, Panda P&D AMP-K PRO
Zippo Lighter Amp