One more thing to add, though I'm not sure it'll help you any. As technology progresses, you'll find you simply need more resources to stay up to date. It's how computers and software work, I'm afraid.
2.0 uses more resources than 1.3
2.1 uses more resources than 2.0
2.3 uses more resources than 2.1
3.0 uses more resources than 2.3
Windows ME used more resources than Windows 98
Windows 2000 used more resources than NT/ME/98
Windows XP uses more resources than Win2K
Windows Vista uses more resources than Windows XP
Unfortunately you simply can't progress and add all the gee-whiz bells and whistles everyone wants without some sort of tradeoff in resource usage. I'm positive we could make IPB 3 just as efficient as IPB 2.3.....if we were working with the exact same feature set. i.e. get rid of friendly urls, get rid of the report center, get rid of personal conversations, get rid of the new skin. But then we'd be on 2.3, wouldn't we?