cylinder heads
 

looking at getting my heads done. i want to get some stiffer valve springs and possibly valves. is it worth getting new valves? i dont have a SC or anything, just naturaly aspirated. what is a good set of valve springs? i dont need that maximum stiffness, just some better than stock springs.whats a good P&P job cost approx? BTW, keeping stock cam.
also, this results in a flatter torgue curve, right? it wouldn't sacrifice any down low power? how much torque, HP gain should i expect? thanks for any info