Attention to detail

If you want gobs of detail in that price range I would recommend the Martin Logan Aerius (i--if you can get it for <$1000). You will sacrifice some of the bass you've gotten from your 603s, but you will gain a tremendous amount of detail, air, and transparency. If you have not listened to Martin Logan's you should to see if they are the right type of speaker for you--they are not for everyone--and speaker placement is very critical.

You may be able to find a used pair of Merlin TSM monitors in that price range. The Merlin speakers are very detailed, yet still very musical.

Are you sure you have the source and amplification for your priority? I am not implying you don't, but one has to really like the what the upstream does when they want to hear all of it.