Hmm, tough one there. I'm guessing yours are the 150 Watt, 15" woofer versions?
The centre channel on most 5.1 soundtracks is used primarily for vocals, so I don't believe you need to match the sheer power of the bass on those speakers to get the full impact.
That being said, I think your best option is to talk to your local decent hifi dealer and see if he or she (why are most audio-nuts male?) will allow you to bring your speakers in and test them out with a range of existing centre speakers. I've never heard those speakers myself, so I can only go off of other Pioneers of the same era. Maybe some of the Klipsch, Revel or maybe even Jamo speakers would work?
The amplifier definitely won't be as tricky to match, but your speakers are used to quite a bit of power, so be aware of just how hard you'll need to drive them to get the best impact. If your budget stretches to it, a pre/power amplifier system would give you power to burn.
I've long been a fan of Marantz amplifiers, mainly due to their sound and general build quality. Value for money is good, but keep your eyes open for some good deals on mid-range Onkyo and Denon receivers too. These tend to have more features for the money, but with slightly less focus on audio than the Marantz equivalents.
Best of luck in your search, and please let us know how you got on.
I have a pair of Pioneer CS-G403 speakers that I would like to use as the front left and right speakers in a 5.1 surround system. As such, I am looking for a center speaker that will acoustically match these. Any suggestions? Additionally, I will be buying a new receiver for this setup (finally upgrading from 2-channel audio). It shouldn't matter if I choose a non-Pioneer receiver, correct?