You won't get a faster connection from assigning a Static IP address.
Also, you can just DMZ to the 360, which is easier to do. And there is no security risk DMZing to your Xbox 360 because no one could careless if you got all the ports open on your 360
How much traffic you shooting for on the rig?
If you are wanting to put a cheap rig together for a pretty fare price, you can hit up Overclock.net F/S section. People are selling stuff really cheap on there. That's where I would start if your wanna keep it a fairly cheap project.
Shoot for...
I would use some WD Green drivers, 5400 RPM and 64MB of cache. Although 32MB of cache vs 64MB is not much of a increase performance, it will help in a NAS.
Also, RAID 5 requires a minimum of 3 drives
I haven't ran a NAS before, but these drives should work fine.
If you will be uploading to...
I will stay with Imageups still, I've tried Flickr, Photobucket, Tinypic etc and I don't like them much at all with the restricted file size, max resolution etc. If you could implement user accounts great, if not then I can adjust to that
I like script a lot imo, nice and clean, simple.
Also, might want to look into the script and it allows easy changing of image size, because remember I asked for the 5MB limit for photography but the stupid script kept it at 2MB.
EDIT: now I noticed no user accounts >:[