In reply to jack_44:
Depends which theatre. Most modern theatres have seats that all have a good view. However many of the older theatres may have restricted or limited view seats. Avoid these if you want to impress her. Something worth bearing in mind is that the performance is usually delivered to those in the stalls so even if you have a good balcony view, you may feel somewhat disconnected from the performance. You pay for what you get. That said, if you just want a cheap experience you can't go wrong with the cheap seats. My mum and I went to a ballet at the Paris Opera House for €6 each, but had to stand on our seats to see anything. Still an amazing thing to see in an amazing venue. We left at the interval having had our fill.