I'm looking to upgrade my hifi to the Nad c352 and Nad 542 cdplayer. However, that will already have blown my budget.
What I'm wondering is how badly speakers age? I've had some Mission700's for about 4 years, and they were a pretty decent speaker when they came out, but have speakers moved on immeasurably since then (would the B&W600's or Wharfedale 9.1's be a huge improvement?), and even if not, would the Mission's actually disgrace the new Nad stuff?
As for them being on par with the models you mentioned above is totally dependent upon your ears and preferences.
I could say yes they are on par with a lot of other speakers but your ears may tell you different.
Upgrade your components first and see how you like the speakers you currently own. I'm betting that you will like it, and I certainly doubt that it will disgrace anything.
Speakers have not moved on immeasurably in the last 4 years. That said the Mission 700 was not a particularly fine representation of the breed. B&W DM600s and Wharfedale Diamond 9.1s are both in the next league up from the 700s, so even in your current system they'd probably provide quite a boost in performance. That said, you're probably better off going with the electronics first since garbage in equals garbage out. The electronics you've chosen is very good indeed and will make your Missions sing as well as they can. The Missions won't disgrace the new kit, but they won't let it shine like it could either. Eventually (next year?) you'll upgrade to round off the system.
Right. I think it'll be a case of gradually upgrading the speakers then. On a slightly different note, I'm not going to be able to place the new speakers on stands. Of the two models I'm considering, one's front-ported, the other rear. Assuming I can't demo them at home (highly unlikely), should I go for the front-ported 9.1's on the basis that they'll sound better placed against a wall? Or is the difference going to be minimal?
Not really tricky. If the speakers are going against a wall then I would look at front ported or sealed designs. There are plenty out there. I would also like to second what Frank said. Upgrading the electronics first looks like the best move.