I haven't heard the Ue900 but to me the Tf10 mid is bit too laid back for great prat. It has a very articulate high end and bouncey midbass so it's relative. For me IEMs with too much midbass will cloud crispness in the mids but others like lots of it so you need to listen for yourself. The GR10 has about 5db more midbass than an Etymotic and that much less than W3 for instance so you'll need to decide what works for you. Similar overall quantity to a w4 but less upper bass. Being a single driver, it tends to have good timing and PRAT. It's not perfect but none of these are. From goldeners:
What this comes down to is that the Gr10 is a viable contender but that you need to decide for yourself if it's for you. It doesn't cost more than the very popular and also plastic W4, Shure 535, Ue900, Pfe132 etc and measures as well overall. It's not overpriced for what you get but whether it's what you want to get is an entirely different question. I stopped juggling universals after getting the GR10 and decided that I needed to get JH13s to make a noticeable jump up.
Edited by goodvibes - 12/13/12 at 8:00am