Yamaha RXV-630 Good enough?

If you are using this system primarily for HT, it would be fine. For high quality 2 channel you are going to want better quality than this for electronics. Maybe a high quality integrated if you are not willing to go the separates route.

I use the rx-v800 with the paradigm monitor 11's and it is simply amazing!

i'm no expert, but i run a yamaha rxv3000 and i use an acurus 125x5 to power my system. i had an acurus a150 powering the mains, but picked up the 125x5 at a deal. i have been extremely pleased. the yamaha will do fine, but i feel better using it as a preamp.

The Paradigm's were the Monitor 3's (I think; but maybe the Titans) They were $650 for the pair. Does this sound right? The Paradigm's sounded amazing but they were in a huge home theater room at the store and were hooked up to $10000 of equipment.
If I add an amp to my receiver just to drive the stereo speakers for music and use the receiver's internal amp for the remaining speakers for 5.1 what would you recommend that would fit nicely with the Yamaha. (under $500)

Yamaha products tend to be bright so I would avoid pairing them with metal tweeters such as the ones in the B&Ws. Try to audition them before you buy and see if you like the sound. I have a Yamaha rxv1000 receiver and used them with PSB alpha speakers (metal tweeters) and the sound was not great.

Some people may disparage Yamaha, but they've always built solid, dependable gear, and your receiver should drive the 602s without difficulty. (I'm assuming you aren't trying to fill an arena with rock concert-level sound.) The soundstage will be as good as your speaker/room combination will allow. The Yamaha will not be the constraining factor here.

As for the speakers, it depends on which monitors you mean, but both B&W and Paradigm have good reputations. One is not better than the other, and you should to listen to both and decide which YOU prefer.