If you do want better prices be sure to ask an Apple employee at the store if you buy it there about end of time macs to get a GREAT deal. Or if your shopping online check out macmall.com and Apple refurb.
You should try running an ethernet cable from the router directly to the 360 so the internet will be more fast and secure. Hope it helps :)
Also maybe the router is busted and you may want to get a new one, if thats an option for your budget.