Balanced armatures, especially single balanced armatures, are typically brighter than a dynamic driver. I started this poll because I actually preferred a brighter sound sig, and couldn't find anything I wanted for cheap in this price range.
I own the A151. They sound pretty good my only gripe is the tip slides off really easy. Found a suggestion to tie a piece of floss around it but I have yet to actually get floss (I just use mouthwash or on occasion those little mini floss thingys)
Actually...
Since it's been a while I just hooked them up to my mac mini (straight in, no amp or dac or anything) and playing ETN.fm trance station (I'm familiar with that and it offers a good range of highs and lows). The A151 definitely aren't lacking the bass, I'm getting a little bit of the phantom vibrations even and this is at a modest volume. The important thing with BA's is to get a tight seal. Not having a seal would be my first guess as to why @hakushondaimao would be unimpressed with the bass. Sure enough the amazon page (http://www.amazon.com/MEElectronics-Balanced-Armature-In-Ear-Headphones/dp/B004OBZ2XQ) mentions that you need a good seal for bass. I'd highly recommend them for the price. That said when I took them out both tips stayed in the ear, that's why I don't wear them more often. But they are good at sound isolation. I keep them in my laptop bag for when I'm working at datacenter which for those that have never been at a datacenter it's loud.
(update) Looking at the amazon page and others have mentioned the Comply T-100 tips, may give those a try to see if they stay in any better.
(update2) I've since bought those comply t-100 tips and those tips aren't sliding off any time soon. It did get rid of the bass a little bit (likely due to the insertion depth changing) but it's still fine and solves my main gripe with the A151