Bring some CDs with you that you're familiar with, and understand that if you do buy something, you should be able to get 15% off MSRP, roughly. Also, I assume you'll need some stands if you're getting bookshelf speakers? I know Paradigm's stands tend to be expensive; but I'm sure they're built well. (For reference, I spent $65 on a cheaper pair of stands I ordered online; they don't look nearly as nice as the Paradigm ones, but they saved me at least $100 or so I bet, and the speakers will be going in the back of the room eventually anyway.)
Also, listen to as much stuff as you can. Like I said, you may be happy with the Mini Monitors or something, or maybe you like, say, B&W better than Paradigm (personally, I listened to their 705 bookshelves and wasn't impressed, but that's just me; plus I still want to hear the CM1 and 5's). And if you're happy with a $400 pair of speakers, why get the $1000 pair?
I'd try and listen to the speakers with and without a sub too. IMO a sub can really change how speakers sound (even in the higher frequencies); it's weird.
You said you can afford to spend $3500 on the front 3 speakers? If it were me, I'd consider putting some of that money toward a sub by HSU, PSB, SVS, or Velodyne, to name a few (on a side note, Paradigm's subs aren't very well liked for music; they're much more oriented toward being boomy for movies from what I've heard; if that's what you want, they're not supposed to be too bad). The rear speakers you currently have are probably fine, depending on how much you watch movies and how picky you want to be. Even if you wanted to replace them though, $1200 or so would get you a pair of Mini Monitors for the front, a CC-190 center channel, a pair of Atom Monitors for the rear, and a decent sub by any of the above companies.
Oh, one more important point. I'd consider jotting down some notes as you listen to the speakers (e.g.: guitars sounded good on these, these sound funny in the higher frequencies; stuff like that). I wish I did this last time I went to listen to speakers. You'd be surprised how quickly you forget which speakers are which, and what certain ones sounded like; especially if you listen to a lot of them. With notes, you can come back and tell us what you wrote down, and we can help narrow down your options (or give you new ones) based on that.
Good luck, let us know what you think.