Its hard to personally recommend others as I've not used them.. the DIR-825 is also great but probably about the same price.
http://support.xbox.com/support/en/us/n ... pment.aspxAnything on the above link should work if you ensure you get the correct firmware for it that is listed.
The Netgear WGR614
v8 will work with the correct firmware and should be cheaper but I think they are on version 9 now so you might not be able to pick up an version 8 new
You won't see an improvement for the Xbox at 1000 no , but if you are doing big file transfers/streaming etc on your PC's (wired) and they have 1Gb nic cards yes you will