Customs are the best you can get, but how much better they are seems to be quite small in some cases, but I've not read enough about them to really comment.
The Triple's have great highs, which are crystal clear, unlike the Shure's which are renowned for being rolled off, but they have a better bass, because of the warm sound that they have, although the Triple's bass is more defined and punchy for me.
For me, the W3's have highs that are very close to those of the Triple's, but also have the bass of the Shure's, without being too warm sounding, which is what I was after.
As I said earlier, I went for the
ACS custom sleeves which cost £89.99, including the price of an audiologist visit for the impressions, a choice of colours and all postage. This way, you get the same earpiece as the customs, but at a fraction of the price and it was well, well worth the money in my book.
If bass is a big requirement, then you should also look at the Sennheiser IE8's, which are supposed to be rather bass heavy, although they do lack slightly at the high end. But I've never heard them myself, so can only comment upon what I've read at Head-fi.
Also fit, the Triple's do stick out from the ears a bit, although you can swap the cables round, then they fit better, but nowhere near as flush as the Shure's or W3's. You can also buy spare cables for the Triple's for about £17, which is very handy.
There's a lot for you to think about mate, all those I've mentioned are quality phones, but each have their own sound signature and it's not easy, hence me having bought three pairs, until I settled on the Westone's. But what's great for me, isn't for the next person, plus the fact that I mostly listen to metal/rock dictates my choice, also I also listen to some regular pop music, which also sounds amazing.
You could also do what I ended up doing, buying a second hand pair from the classified section on Head-fi, or on here, although top end phones don't seem to pop up that regularly on here.