In a daylight it does help when you set the brightness to full (or higher than average), but in general the visibility/readability of the screen is pretty good to my eyes (i'm not making general statements, this is my perspective
).
Yeah, playing with impedance does affect the sound, but it's on case-by-case basis with iematch - in some it improves, in other it could change the sound where you prefer tonality of the original. Not sure which iems you refer to. Btw, between SE and BAL of dx120, even SE has a wide enough soundstage, while BAL expands it a touch wider. With those selective iems where you would hear hissing with dx120, it's attenuated going from BAL to SE, but it's still there as I mentioned at the end of my "under the hood" section in the review. It's a mild soft "waterfall" type of noise floor hissing effect. I'm not gonna BS with "black background" or "it's not a big deal" because we all have a different ear sensitivity. I review not to promote the product, but to describe the product so people can decide for themselves if it's their cup of tea
It does affect a few iems, and some people will hear it, other won't. Based on my experience, I hear it mostly with volume down to zero using my sensitive iems and when I raise the volume up to a normal listening level - in my cases it's not even noticeable. The only IEM where I find it to be a problem is Andromeda, but as many would know, Andro hisses with many DAPs. I only had a brief listening with Andro earlier, not enough to write impressions, and now it's out for repair (mmcx connector broke on one side).
If you have SE headphones, you need to buy BAL terminated replacement cable (if your headphones have a removable cable). You can't use SE to BAL adapter, you will short the output of the DAP because in SE (TRS) wiring the ground of L/R side is connected together and you can't split it to BAL (TRRS). If you can replace the cable and go balanced, higher output power will improve the efficiency of your headphones, since you don't have to push volume as high. In some cases it helps by providing more volume headroom, to eliminate some possible distortion.
Unless we have a different definition of what is "dry", I don't find N5ii or N5iiS to be dry. In music production, "dry" refers to when you don't apply any effects (no reverb, chorus, delays, etc) - that's a standard definition. In sound description, people have their own variations of definition, everything from a fantasy "flows like a water" to a golden-ear "at 7.35kHz the peak of 2.37dB is harsh" LOL!!! For me personally, I associate the sound being dry when it's more analytical, cold, and fast with a shorter decay where it becomes a little more digital and less analog. DX120 doesn't sound like that to my ears (and I always emphasize to "my ears"), unless maybe if you switch to reference sound mode with a sharp filter roll-off. So, in my book, DX120 is not dry, and you can play with filters and sound mode to fine tune it, to "warm" it up a bit.
People upgrade to a new/another DAP because they are not happy with something in their current setup and want to improve either a sound quality, ergonomics, battery life, faster charging, balanced output, streaming, wireless headphones support, more power, etc. If you have DX90 and only use SE output and only care about output power because you have demanding headphones you can't drive efficiently with your current setup, then you should look into DX150/200 and find the right AMP module to meet your SE requirements (that's if you are interested in iBasso DAP). If you're comparing DX90 and DX120 and the only upgrade you are looking for is a higher output power of SE headphone output, DX120 is not for you.
