what version of mac os are you running?
i have 5605 emails in my inbox and my powerbook and imac (granted they are not 2 years old) are handling mail very nicely.
and again, what version of iphoto? iphoto has been notorious for being. . . not fast, but apple has done a good job with iphoto 5 and, for me, it is faster than all the previous version. 6020something photos in my iphoto.