I don't know about configuring the 5-way, but if you got VoiceDial from VoiceSignal you could just say the numbers.
I have no car kit (yet), and I may not buy one. I have the phone mounted on my dash, and in speaker mode (with the radio off) I can talk & hear folks just fine. W/ VoiceDial I hit the activate button (which you choose), and say, for instance, "Call 1-800-555-1212" and it does it about 98% of the time correctly the first time.
HTH