Valerie is absolutely correct. Arcadia Residence is amazing. We were in the attic apartment at Kozna 6 in 2012. We booked 8 months ahead for them. I think she's referring to the apartments on Kozna 6, as they have others in other locations. If you are talking about Christmas 2015 I'm afraid you are out of luck for Arcadia Residence. They are a very popular place. Just for fun I emailed them a couple weeks ago about dates in late December 2015/early January 2016. Didn't even get a reply. I ended up booking this apartment at Municipal House:
https://www.airbnb.ca/rooms/7333213
From this apartment its 7 or 8 minutes walking to the old town square to the west and same distance to the main train station to the east.
There are tons of restaurants throughout the old town area. No specific recommendations.