Honestly, I hesitate to really pass sensible comment as, while loving and appreciating quality sound I find it very difficult to quantify and describe it - especially in the accepted terms of this forum.
I can do no more than this:
I've owned (in recent memory) 5 sets of iems.
RE0, RHA-MA350, HisoundAudio BA100, GR07BE and these DN1K's
All these are what I'd describe as way above iPod generic earphones/buds AverageJoe may own but not in the high, high end.
In my ears and listening to my music (80% Electronica - less Dance Music these days but more Ambient, FSOL, Leftfield, GoldFrapp, BoC , DownTempo etc. Head Nodding rather than leaping about the place
(I guess still, often, containing the sorts of bass-lines of interest to you.)
I'll try and compare them in terms of 'bass'
(From Most to Least: )
RHA-MA350 >> DN1K >>>>> GR07BE >/= BA100 >>>>>>>>>>>>>>>>>>>RE0
Memory tells me there's not a huge difference between the 350 and the DN1K but I don't have them with me right now to test one against the other.
The DN1K however has THE most amazing sound-stage and instrument separation, details too, that I've heard in an IEM (again - please - I'm no expert but know when something makes me smile!)
If I'm instinctively looking around as sound kicks in then something is right with these. I couldn't be happier - they seem perfect to me but I wouldn't say they're shaking my teeth out with sweaty club bass-lines - there's loads and it's plenty for me.
I've liked all the IEM's from that list -
The RHA as a cheaper, but quality sound for rougher handling - (Can't beat the 3 year warranty)
The RE0 were my first move into quality sound in an earbud - still amazing for acoustic music.
The GR07BE were amazing, I loved them, listened to them everyday until the left channel stopped working 11 months in. As is written widely - 'Bass Edition' is a misnomer - They're just bassier than the Mk2 by all accounts.
The BA-100 are what I sleep in, cheap (I got the deal when bought in black) but nicely detailed sound and clarity at low volume for drifting off....
I also own Symphones Magnum V5's and Allessandro MS1's
I'm listening through a MisterX Y1 and Mini3 or an Ipod 5.5g and Mini3 (as well as unamped straight out the 5.5)
I haven't had time to try everything out yet - the spacers etc. I'll try the reds and Foams today - mostly I've been on the blues and wide gray turbine-like silicone tips.
Please take the above as my thoughts and not advice as such, I'm not versed enough in sonic description to offer more.
Thanks for the review. Once you switched from the large tips to the medium tips, how much more bass did you get? and did different colored spacers change the bass amount too?