yet another update:

i decided to install another fresh copy of 10.5.2 rev1 on a spare partition just now, but this time i am using nLan for ethernet (forcedeth) instead of my marvell (skgeosx), which I have now disabled completely in BIOS. everything else is totally pure on this installation except for the video kexts i need to modify for my video card to run. i also updated leopard (including the new safari 3.1), and patched everything with marvin's. for now, i've decided not to install AppleSMBIOS-27 or the fixed IONetworkingFamily, and i am leaving the mach_kernel at the default 9.2.0. if i get problems with this setup, i will replace the AppleSMBIOS and then try the fixed IONetworkingFamily. as a test, i will be downloading a 3GB torrent with bitrocket and little snitch running. may leave it to seed over night as well. i'll report back with my results when i find out something new.