i go with wired connection, firewall low, xbox ip in the dmz, no static ips or port forwarding etc. just keep it simple. its the best setting iv had and iv tried them all. tho i still get lag/latency etc but thats mainly vm. :-s
first thing i would do reset the modem get a pin press in for 10 all blue lights will show let go,now go to fire wall and set it too OFF , then set wireless too 300 , if u want wired make sure u get cat 6 cables not cat 5 as this gives u faster data speeds . then check ur wireless for how many peps are using the same number as u so try this http://www.metageek.net/products/inssider/ u may have too change wireless channel
In addition to what weeman stated above, CAT5e cables are also 1 gigabit capable. Just make sure if you choose to buy one that is has the "e" on the end if you do choose to buy a CAT5e. Even though I suppose CAT6 might indeed be better.
I hook up through a CAT5e and get 90mbps - 107mbps download speed about 99% of the time i'd say. Lucius.