I'm addicted to metal as well. I was in the same quandary as the OP some months back when I was shopping for a pair of iems for portable use. I had almost decided on buying the TF10 but by a very very lucky chance and thanks to Sylaw, I was able to get a Westone 4. Though my initial ownership hadn't been smooth (left channel didn't work), I was lucky to have some warranty left and Westone replaced them for me free of cost. They've been working fine ever since and I love them! The details that these things bring out has to be heard to be believed! Bass is dependent on the tips and the seal. Once you get a good seal, there's some finely textured and detailed bass to be enjoyed. It's never excessive, but it's not as bass shy as some Etys either. Mids are its strongest point- smooth, liquid and immensely likable. Highs are again greatly dependent on the tips and the seal. Drums sound realistic, textured and never becomes a boomy mess. Guitars sound crisp and full of definition. Those solos will never be the same for sure. Bass guitars sound awesome too- with the right tips, I could literally sense the strings being plucked in a good recording. Instrument separation is awesome. Easily the best investment I've made in my audio setup. Do give them a try.
Less expensive options would be-
1) The TF10. When I had asked here for a recommendation, the near universal vote was for the TF10. An unbeatable bargain at less than $200 imho. What does it go for these days? $150? Fit can be a caveat as the shells are big. Try them out first.
2) JVC FXT90. Came across as quite highly recommended. Heard that these dual dynamics make distortion guitars sound beautiful. I was also on the verge of buying one after the deal with the TF10 fell through.
3) Vsonic GR07. Widely said to be the gold standard when it comes to reproduction of drums.
4) Westone 3. More aggressive than the neutralish sounding W4. More of a V-shaped sound curve- more bass and highs. Must be great with rock and metal. The sound should be greatly dependent on the tips and the seal like the W4 as both of them seem to share the same shell.
As for amplification, I'm in a sort of dilemma too as to just get a better source (maybe a Clip Zip and rockbox it or a Galaxy S3) or to buy a headphone amp/dac like the Fiio E7/17. Does the Westone 4 benefit from amping?
Edited by lepermessiah - 9/24/12 at 11:55am