I'am thinking of buying some used cornwalls. What would be a good price for a pair that are in good shape ( at least a 8 on scale of 10). I have a pair of RF-5 and I enjoy the way they sound however, I want a bigger sound more punch. I listen to mostly rock (Led Zep, Van Halen, Pink Floyd, etc) Are the Cornwalls the speaker I'am looking for?