I have these and i'm really quite surprised at how well they perform. You do need a good source. But with a good source the sound is really... transparent and clear. I'm not yet ready to make a review... because i just don't have the time, but they are really worth the effort.
as far as bass. They don't lack any more bass than the sleek audio sa-6 iem. However, compared to a sony ex-71 they do lack bass considerably (but let's face it, those earbuds sound like crap)
As for a mod with foams. It isn't a mod, sony supplies a pair of foams for over the bass extension tube.