We have a Bose which offers great depth of sound, even in the kitchen, but it's pricey. Last year my OH bought a Kensington docking station for upstairs and the sound is more than adequate. It cost app £25 from
Richer Sounds. If you have a branch nr you it's well worth taking your iPod (borrowing your daughters) to check out whatever they have in stock as they are always very reasonable. They'll be happy for you to try before you buy.
Sound quality is so variable, and personal, that it's worth checking everything out in person first even if you later decide to buy online.
I've just found
it online - price has gone up to £50 but I'd recommend it.
Here
it is again but at £31.60 - can't be bad!