its hard to say for sure as it doesnt list the speed of the WAN port if but it seems to indicate that its underpowered as that
Netgear RP614UK uses a Processor: 1 x ARM 50 MHz, were as if you look at the 3rd party firmware list for the good netgear they all use far faster CPU's
http://wiki.openwrt.org/TableOfHardware
150MHz through as much as 500MHz today.
you dont say what modem you currently have but its got the cm-10240-384 so your on the tw part and its set for 10Mbit down, 384kBit up right now.
i suspect the routers slowing you down but you can test it easy enough , just get a second network card inside your brothers machine and set that up as the master machine and have yours go to it direct without the router in place.
BB<===>brothers-netcard1----brothers-netcard2<===>your machine
ohh i see its been determined V2 is it, i supose thats why its got the really slow CPU.