You most definitely want the from three to match, generally from the same manufacturer/line.
The rears are less critical than the front three since they rarely contributr too much to the overall soundscape. Those Pioneers will be fine.
Also, get a better subwoofer. The better the sub, the more you will be satisfied with your system. Try one from some of the main ID types: Hsu, SVS, etc... Lurk the subwoofer forum here for some clues as to what to look for.