25mbps wireless LAN connection

Hi,

I'm just wondering before I tear my house apart if anyone can suggest a wireless fix instead. I recently installed four 1920x1080p resolution security cameras at my home. Everything running to the gigabit switch and 10/100 router and then to the server is absolutely great, with only an almost unnoticeable lag in camera response. Doing a hard connection to the router for the client works very well also. I then moved the client PC upstairs (about 50' away with the router in the basement), set it up on the wireless network and of course, everything went to pot, with about a 5-8 second latency when I give either of the PTZ cameras a command to move. Knowing that I would have to replace my D-Link DIR615 router with a more powerful one, I bought a DIR825. Set that up and everything got worse, including the hard connection to the server, which leaves me to assume something is wrong with the router. So I reinstalled the old 615 and am back to the beginning again, with almost zero latency to anything hard wired. What I am wondering is if anyone could recommend a powerful enough wireless router that would transfer data at a high enough rate to mount 3 client PC's (25mbps connection required for each) and have them operate more of less seamlessly? The other alternative would be to hard wire everything, but that will be an unbelievably nasty job in this house. All of the Client PC's will be within 50' or so of the router, but with a floor and about 3 walls in the way.