i use the P5's which in treble and midrange character are identical to your P4's. I upgraded my amps by going with parasound.
i use a pair of HCA-1000A's on my fronts to biamp and a 1203 for the centre and rears. But you could always try a 1205, or 2205 as a way into parasound. Ive found them to be a great match for teh B&W as they dont have problems with the B&W's nasty impedance dips.
The P4's like lots of clean high current power. so try to find something with plenty of current.
i use a pair of HCA-1000A's on my fronts to biamp and a 1203 for the centre and rears. But you could always try a 1205, or 2205 as a way into parasound. Ive found them to be a great match for teh B&W as they dont have problems with the B&W's nasty impedance dips.
The P4's like lots of clean high current power. so try to find something with plenty of current.