I've had a fun day today where I played with some speakers out of my wife's Jazz which has Gathers 60W 2-way 6" speakers all round (factory upgrade option).
Results were interesting. Putting the Gathers in the rear improved power handling a small amount but actually lost bass which surpised me. So I tried them in the front and they cleaned up the sound nicely. As they have the same mounting system I clipped my old fronts into the rear of the Jazz and everything is sweet. No grief from my wife as yet..
Still keen on changing the rears but I think some careful mounting needs to be done to get the best out of them.