Hi Michelle,
As for the band in the Butterflies Lounge, they are great. They are called Music Network and they do classic 60's, 70's & 80's music, along with some others thrown in. If you like music from Beatles, Lynyrd Skynyrd, Queen, Led Zeppelin, Journey, Def Leppard, Nickelback, Jimmy Buffett...then you'll enjoy them. Tell the boys Janann says hi.
Now for the room, on the Spirit Class ships, I've only been on the Legend and had room Riviera 1154 and I thought it was a great room. I have done a guarantee room before, but I did't get a room assignment until I got to the cruise port to check in. All the other rooms I have selected when I booked. I'm a travel agent and as far as I know, once they assign you a room number, it's not likely that it will change. Usually if you are going to be upgraded, they do that when they give you your room assignment. I don't think you'll have a lot of trouble sleeping. I know my friends played until 1 or 1:30am on other ships, but on this ship, they only play until midnight. As for the Karaoke I can't imagine that going really late into the night and once that is done, they close that lounge down so there wouldn't be anything going on it there.
I have been on the Empress deck on other ships and I love that deck also. It's middle of the ship so it's a great place to be. Either way, I think you are going to have a fabulous time on your cruise! Enjoy!
Happy Sailing!!

Future Cruises:
Carnival Legend - September 2009
Past Cruises:
Carnival Imagination - September 2008
Carnival Legend - October 2007
Carnival Imagination - January 2007
Carnival Imagination - September 2006
Carnival Fascination - May 2005
Carnival Imagination - November 2004
Holland America Zuiderdam - May 2003