The 7800N has superb wireless coverage/speeds. Have a look at this review where it trounces all rivals:
The 7800N uses a Broadcom (6358) chipset which are widely ackknowledged to be the best in business. You can also alter the downstream SNR margin to give you a higher or lower sync speed. Can't comment on the gigabit port speeds as my wired LAN is only 100mbps.
If you still don't think this router is the dogs danglies then have a look at reviews on Amazon:
TalkTalk Plus LLU ADSL2+ connected @ 17612/1019 kbps
Attenuation 27db down / 9db up
Noise Margin 3.3 db down / 12db up
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