I have been to prague and shown around for 3 days by a native.
It is an amazing place, and as reports suggest very competively priced , If you wander away from the tourist areas the prices are remarkable - 5 of us had lunch with lager , a tenner!!
I would steel away from the main drag and stay in the old town or up by the powder tower - the castle side may be a little too far out.
I have also been to Budapest , in my opinion this had a bit more history then Prague but was not as quaint.
Prices were very good even on the main drag.
A slight word of warning however - Prague seems to be a victim of its own success - we stayed wed/thurs but on friday morning and at the airport hoards of stag partys were arriving- If you want to view this beautiful city without numerous male flashers go midweek
I also love amsterdam but price wise I found it at the higher end and more of a bloke place.
Barcelona is very good - plenty to see