Hey Laszlo, just responded to you in the other JBL thread. :D
With that plan, you should look at the S412II. They're a bit pricier, but if you think you're going to go without a subwoofer, that'd be the option I'd take, especially with a 70% music mix and only 30% HT.
It depends on a lot of factors. I A/Bed the ND310 and S310 in the store and the N surprisingly sounded better there. It sounded like crap at home. I got the S310s and A/Bed them with the Ns at home and they sounded much better. I eventually went with the S312 to get more full bass, but the...