First of all, if you don't mind, could you elaborate on what you find missing in your existing stuff(apart from Garritan)? I use Logic so I know that it's sample library is impressive to say the least. In fact, whenever I looked around for upgrades, I merely realized that I wasn't using Logic's stuff to the fullest. So it might help if you explain what you find missing in your current arsenal.
I could help you out a bit with drums though. Ultrabeat isn't very great for realistic drum sounds in my opinion. You basically have BFD, Addictive Drums, EZ/Superior, and SSD among the popular products. Many more exist, obviously; but these get the most rep. Out of these BFD is the deepest, most complex and most tweakable, and not the easiest to use. Toontrack's stuff is much easier to use, but their drum sounds are already preprocessed to some extent, and you can only tweak them so much. Addictive drums falls in between. I've only used their demo but I liked it. It's deep enough to give you some sound control and simple enough to not to interfere in your composing/producing. I don't know much about SSD.
If you want really cheap I guess BFD Eco(their stripped down and simpler version of BFD, which I have and like) would be it, but I don't know how you'll take to it. BFD (eco) requires time to learn how to use it to its best, even though it's much simpler than it's big brother. It's almost like mixing a real drumkit, I guess. You have to know what you want.