I've just fitted an IronGear P90 into a USA Hamer (in the neck neck position) to replace a Seymour Duncan made P90 that was a bit too powerful and 'thick' sounding and I'm really pleased with it. Not expensive at all. http://www.irongear.co.uk/irongear_pickups_010.htm
But I'd guess that the Tonerider P90s will be of similar quality and sound. http://www.tonerider.com/p90
Of course you can pay a lot more if you want to get that 10% of extra tone (and I will do for my ES330 build), but there are a lot out there and I'm just as confused as you about what to get when I look around.