i use V's on front and back of my mod and did on my stock till i sold it. I like V brakes better then HS33, they seem to hold better in my oppinion and the leaver seems easier to pull in if you have a decent cable.
i ran on my stock SD7 callipers on the back with SD7 leaver and on front Shimano Acera callipers with SD7 leaver. both with clark cables this was a awsome set up.
on my mod i tryed running the same set up but the SD7 callipers were two small for the back wheel so moved them to the front and put the Shimano Acera callipers on the back as they were taller. I find this set up even better then i had on my stock.
So in my oppinion, yes it would be a waste of money. I rate the Shimano Acera callipers more then the SD7 ones and they are the cheapes ones on tarty i love the SD7 leavers though they are ace, work well and are cheap.