first time hack, a few questions

alright, i have decided to take the plunge into the hackintosh world. from a little quick browsing i have found that my hardware seems to be fairly well supported. i am running:

Pentium E5200
Gigabyte EP45-DS3R
8GB DDR2
Sapphire HD 4850
WD Caviar Green 1TB

I have purchased a retail DVD of 10.5.6

I want to be prepared as possible when the time comes to install the software. I would like to use EFI to help avoid issues with updates and the like. i am a little bit concerned about weather i can get my ATi 4850 supported. if anyone can point me in the right directions for things to look out for to help make this work with a minimal amount of modification that may break when i update to 10.5.7 or later. I have a spare usb drive hanging around that i would be able to use as a permanent attachment to the back of my computer, i noticed something called EFI-X which doesn't seem to be much other than a USB drive. I have heard of people being able to boot directly from thier drive and having time-machine working. this would be optimal if at all possible. sleep would be nice, and SOUND is a must. I really appreciate your help. I just want to make it throught the install the first time with as few (unforeseen) problems as possible.