Any advice on speeding up iTunes?

I currently use iTunes as the central media hub for my home. I have Apple TV units in each room, and use Home Sharing to stream media throughout my house. My question is this, is there anything I can do do speed up iTunes itself on my PC? I currently have a very large library (42,000+ songs, 100+ HD Movies, Home Videos, etc) and I believe that is adding to my issue. I would try using another media manager such as Winamp or MediaMonkey, but then I would lose the ability to stream media to the Apple TV's. I have a powerful PC (Quad core 2.8GHz, with 8GB RAM, and a 64 Bit OS), can I possibly allocate more memory to iTunes specifically, since that's usually the only application running at any given time? At this point I have 20-30 second delays just selecting songs and adding them to playlists. Any advice is appreciated.