efficiant speaker with good bass?

I am looking for a pair of easy to drive speakers that have excellent bass response for rock music as well as good imaging. At the moment I have a pair of B&W CDM-1 NT's driven by a McIntosh 6450 integrated. I need a little more punch than what I have right now. I have had 2CE's, VR4jr's, Tylers, Meadowlarks & Triangles. I loved the VR4's the most & felt the Triangles had a simular sound to the B&W's but lacked the bass.
I need to stay around $1500 used & eventually want to try some of the low cost tubed integrateds in the 40-60 wpc range hence the reason for higher efficiancy speakers. I also want to switch back to a tower speaker.