Man. This Geek Out 450 is seriously good. I love my HD600 out of it. With the 3D. HD800 and UERM are great with the 450 too, for the most part...
HD800? I can use it straight out of the 450 for most music. Straight out of the Geek, I like the 3D setting. If the treble is a bit much with some recordings, I tried 450 into the Vali. Found that I prefer maxxing out the Vali volume pot and using the GO digital volume control for volume when I do. Anyone else find that cleaner too? With Geek Out into Vali, not sure if I like the 3D. Combo is slightly more relaxed, not as clean overall. Seems to compress some dynamics to get that more laidback sound. Not bad, but think I'l just use the HD600 when recordings don't suit the HD800 rather than using the Vali in the chain. If you are a bass person, you may prefer the GO 1000. The 1000 bass adds some impact and the 1000 treble adds some attack. Fun but can be fatiguing for me, depending on the music. Using the 1000 to Vali still has a good deal of attack on the treble with HD800 (noticeable on certain recordings).
With the UERM, the GO 100 has the least amount of hiss (barely noticeable). The hiss is so low on all of the units that I don't think it is a big deal for most people. I think I prefer the 450 with UERM over the 100 even though it has less hiss and the 450 is slightly brighter tonally. 450 handles the mids to upper-mids to treble transition the best to me and works with HD600/800. Differences in tonality are slighter between 450/100 and greater between 1000/450. The 100 noise floor is not different enough to justify keeping it as dedicated UERM GO. With more use, I might be able to differentiate the 100 further but I just wanted to test with it <enough> to see if it warranted buying one in addition to the 450. (I'm sure people will like the 100 too.) NOTE: The 3D is not usable with iems until it gets quieter and cleaner, IMO. The 1000 tips up the low bass and the treble with the UERM and the HDXXX.
I'm lucky to have the chance to pick nits and compare these three units with my phones the way I plan on using them. I think people will enjoy any/all three Geek Outs (four if you include the 720 that I have not heard). I was looking for any reasons to keep only one.
Bottom Line: Since I am plunking down for the Geek Wave X DAP (indiegogo campaign), I plan on selling the 1000. 100 not different enough from the 450 for me. Hoping there is <zero> hiss on the Wave X with UERM and that the 3D is quiet and can be used with iems. 450 rocks for my uses. Versatile, resolving, tiny, inexpensive. Will bring GO 450 > HD600 to Bay Area July Meet to show it off.