It's certainly true that you get better value out of the centre, but for a special occasion you might well want to go to somewhere a bit more upmarket; it still won't break the bank. Do you want traditional Bohemian cuisine? If so, the Zlaty Dvur in Jilska Street (just off Karlova, in the Old Town) has excellent food and service and is usually fairly quiet except in the height of summer. The Cerne Orel in Mala Strana has a nice old-world Bohemian atmosphere and serves good value traditional food, and has a courtyard which is nice in the summer. If you can give me an idea of the kind of place you're looking for I should be able to make a few suggestions - I know Prague pretty well, and I can certainly recommend places to steer well clear of!