I'm taking the 3/4 class at Parliamo right now, and it's great! I don't know about 'reasonable' - if you mean cheap, it's not, but it's a great class and a reputable place.
The classes are a great and not too expensive way to get a very good handle on Italian. Taught by all native speakers. I became conversational after a semester with them.
Thanks for your input! Gotta learn me some Italian. For the most part, I understand what I am singing, but it would really help to be fluent, especially when after a performance people come up to me and start speaking to me in Italian. It's so embarrassing when they think I am a speaker b/c my diction is clear and I tell them I don't speak Italian!