A rim will be cheaper then buying a wheelset. Yes a wheelset is 'more for your money' if your looking at building up a whole wheel. If you feel you dont need knew hubs then dont bother with a new wheelset, just buy the rims you want and get them fitted.

Call up a few LBS's tommorow (to get a rough idea of general costs) and ask how much it would cost for them to build re-build your wheel/s with a new rim/s.