Networks New House, New Network Issues

We have just moved house to a large old fashioned stone built building. Our existing hardware consists of a DG834 and a WG602 Access Point.

Existing kit:
Netgear DG834 Router
Netgear WG603 WAP
3x Desktop PC's
4x Laptop PC's
1x Xbox

We had it set in our old house so the router and AP were downstairs, providing just the laptops with wireless networking. There was a cat5 cable running up stairs to provide all the PC's and Consoles upstairs with standard cabled access.

In our new house, we want to have the router downstairs where the master phone socket is, and have it pipe wireless round the house. The problem being a deadspot in the furthest room of the house (my brother room) and my xbox/pc are cabled with a 5 port switch.

I've looked into the most cost effective way of doing this and i'm stumped. I don't really want to use the home power things, as I'm a bit dubious of its reliability. Is it possible to use the DG834PN we're about to buy to transmit the signal to my WG602 to give my PC/Xbox wireless access and also boost the signal to my brothers room?

Does anyone else have any better suggestions (Not cabling unfortunatly)

 

Get bigger antenna ie from maplin or can you put an access point outside his window, make sure it sealed up tho.

 

I've thought about getting a 6db aerial, but we'll see.
My dad's gone against my advice and gotten the BT Broadband "Option 3" with home hub and voip phone.

Bit the bullet, and bought these
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=250011455630&ssPageName=ADME:B:EOIBSA:UK:11

 

BT ewwwww whattta mistaka to maka