I have visited the Grand Opera House York on several occassions it is a lovey old venue and it gives you the feeling of being nearer the act on stage unlike large areans.  Being just down the river from Ousegate bridge before the famous pub that is flooded each year and next door to a great italian restaurant. Being within the town makes it an ideal location for making a great night out have a great meal then enjoy a great show.
I must add this is the only place I have been to that I have seen a queue for the mens loo, being female it makes such a change but do not let it put you off it is an old lovely decorated building.