Sometimes I like to poke fun at stuffs.
But yeah, I guess I'll stop since the rest of all that really belongs in Sound Science.
All I really wanted to say was that beyond the interaction of the headphone and the amplifier, there is interaction between the amplifier and the DAC. So it's good to know all the gears in the equation before proceeding.
Anyway, as for opinions, I currently have a Geek Out 450, and a Neko Audio D100 Mk.2 (this one is interesting, but I won't try to derail thread
).
My subjective impressions are that... the 2 sound very audibly different.
The Neko DAC being... very smooth, silky, and very much devoid of noise or anything else like that. It truly sounds remarkably transparent but without being dry, grainy, textured, or... put another way, it's like music is a river that keeps flowing when I'm using it. Its lack of grain and textures is sometimes unrealistic as I have heard the same tracks on multiple other DACs and heard grain and texture. Not sure what is causing that to happen, but just to say... this DAC has the ability to essentially make any amp that is plugged into it sound like a smooth tube amp that's not warm, thick, or syrupy. Despite the overly smoothed sound, details are very apparent, and can sometimes be a bit unsettling because it's all so very smooth. Also it has a very unique way to present bass that truly brings out the "bass" in pretty much anything. Even a SR-009 sounded thumpy and weighty with this DAC.
In comparison, the Geek Out 450 is a fraction of the price, and gets to about 80-90% of the Neko, minus the silky smooth sound, that last bit of soundstage depth and detail extraction, and... "noise floor". I call it "noise floor", but I don't think it's just that, please go with it for now. What it really is is that... when I listen on the Geek Out 450, I get the "sound coming out of thin air" feeling every once in a while with the right track. Meanwhile, the Neko DAC does it a lot more often, and so individual sounds stand out in the space they are at. This is not the same as "separation", since both DACs can present distinct instruments with their unique tone quite well. I think detail extraction may be related to this, but I'm not sure. The GO450 is noticeably less detailed than the Neko. The GO450 is more "textured", or "grainy", sometimes, though, and I consider that to be more realistic.
But either way, close call. I made it sound like they are completely different, but I must admit... they are very very similar-sounding on a quick swap. The Neko is 10% better where it counts, but it really depends on the headphone I'm using. With the Sony MDR-Z7, I can barely hear that difference, if at all. With the Hifiman HE-560, I can hear the differences more consistently. And then with my Audeze LCD-2, I can hear the differences very plainly.
Anyway, I think the OP would be more interested in this last part:
Neko Audio D100 Mk.2 - $1400
LHLabs Geek Out 450 - $199
Sound-wise, very close, and one probably wouldn't notice in a noisy environment (at meets, etc...). It takes some hard concentration to notice.
So why did I say "very audibly different"? Because I like to poke fun at stuffs.
Okay... seriously, I'll stop.