I'll give it a try this evening as I've also got a Rockbox'd Clip+ - need to track down this track so I can load it. Worst case scenario I can test it out on my Galaxy SIII. Also good to note, bass response on these rely pretty heavily on a good seal, otherwise they can sound pretty flat. You may also want to consider reading up on the Vsonic VSD1 as well. I've not heard these yet, but I have their bigger brother (GR07) and I think at their current price they may be a good option. Joker just posted a write up about it on innerfidelity yesterday:
http://www.innerfidelity.com/content/more-less-vsonic-vsd1-and-vsd1s
Still has a mild V-Shape (less so with the VSD1S variation) but seems like a top contender in the sub-$100 range nevertheless. I like the RE-400 most for it's mids personally, but it can fare well as an all-arounder.
I got very lucky on my MKII because it was a risk purchasing from Amazon Marketplace as listed in 'good' condition. I think the description was talking about the box, which is in sub-optimal condition on the outside. The IEMs themselves and accessories though looked brand new inside...a pleasant surprise. I think for me it depends but I typically prefer to buy new if I can, but aesthetics are not always top priority and I knew that the GR07 was pretty durable ahead of time because I previously owned one. In most cases, you are right and it's especially difficult to evaluate with IEMs. I think the pair I got were for someone evaluating them, deciding they didn't like them and returning them in a short time period - there is virtually no wear. As always, when buying used you must take precautions and expect an item to be in used condition...but I baby my babies
I think the only narrow bore tips that work decently with these are the stock double flange tips - they help to attenuate the treble slightly, but I still feel the tips with wider openings sound best. Also, the Auvio 'Sony Hybrid-esque' tips you can find at Radioshack work decently as well.