Looking to add listening speakers

I'm looking to add listening speakers to my system. I have B&W 606S2 bookshelf speakers, two REL Acoustic T7 (L,R) for my low end. Center channel is HTM6 S2. My AV is Marantz Cinema 70s (7.2). I've looked at the B&W 705s, Wharefdale Super Dentons, and Sonus Lumina II Amator. I would use the RELs to add for the low end if needed. Just a reminder, the speakers I'm looking for are just for music listening not home theater. I will use the others for that. Any advice would be great.