I would get the Asus K8N-E Deluxe board,
If you do get the Msi board, update the bios first thing, and if you want to use the front USB ports, find out if you need to pull 1 wire and which wire it is.
Personal preference is also with Seagate drives, because they are often quieter, and I've had fewer fail.
I am sure you know that socket 754 does not support dual channel ram, and that you are getting that because of price, and OCability, right?
I am in the EXACT same spot as you as far as what I am gonna purchase. I think from what everybody is telling me is that i might save up just a little more to go with a 3500+ setup because s939 is where AMD is going. Either way though the 3400 and 3500 are neck and neck and are sweet @$$ setups.