If you want coverage then multiple WIFI sources connected to a common router with ethernet IS the best solution. If that is what you meant by "few cheaper ones and speed the signal around" then you will benefit. If you have dozens of wireless devices, then splitting them among multiple WIFI sources (again connected by ethernet cable) is the best answer. If you have some REALLY old or REALLY slow (wireless G or B) then segregating them to their own WIFI source can benefit the devices hooked to another.
IF you need high end router features then spending more for your core router (and WIFI source) can benefit you.