Need help/advice with my home network....

Ok here is my setup: I have a 4mb interet connection that is in my loft. It is a straight cable (no modem) that gos to my Netgear RangeMax Dual Band Wireless-N Router (WNDR3300). My computer is connected via ethernet cable in one of he ports on my router. Two levels down in my living room I have a Tivo< PS3< and a Xbox 360 . The tivo and PS3 connect no problem. The Xbox 360 picks up the signal via a LinksysWireless-N Ethernet Bridge with Dual Band (WET610N). The problem comes while I am gaming. Im not sure if my range is long enough but I lag alot. Is there something else I can buy. My router andethernet bridge I have had for a couple of days and can still return. If I could hook it up with an ethernet cable I would.