TRy these earphones
[url="http://www.ultimateears.com/_ultimateears/store/products/superfi5eb.php"]http://www.ultimateears.com/_ultimateears/.../superfi5eb.php[/url]
They sound great for plenty of bottom end at a reasonable price, around £110 if you shop around.
They do feel a little bulkier but that's the price you pay for extra bottom end (look at the size of our cabs!!!)
I personally use them on a cable from a small mixer, but agree that if you need to move around you can't compromise on the quality of your wireless system. I've used sennheiser ew300 systems and they seem as good as anything for the money.
BEWARE...I've recently heard that all the available frequencies for IEM and radio mic/guitar systems are to change over the next few years because of the expanding mobile networks. My advice is to but a decent second hand one for now and see where the land lies when the changeover happens. Anyone with the current systems may find them either illegal of with mucho interference!!!