Billion BiPAC 7800N (802.11n) ADSL2+ Router - Signal Strength Question

my mums laptop wireless signal has been dropping out quite alot lately , more then usual.

I have figured its the signal strength because everytime i took it closer , or in the room with the router it would work every single time.

here is my router Billion BiPAC 7800N




i went out and bought one of these D-Link 2.4GHZ Indoor 5DBI GAIN OMNI-DIRECTIONAL ANTENNA




the 1 antenna didn't seem to boost the signal strength on the laptop at all. or to a noticeable degree. so heres where my questions comes in.


Q) As this router has 3 x external antennas , does this mean it would require 3 of those D Link antennas screwed onto it for it to boost the signal strength ?

the laptop is wireless b,g,n compatible , so is the router. i have both router and laptop running in b+g+n compatibility mode


cheers

well does anyone have experience with multiple external antenna router and omni directional antennas then ?

im just trying to find out if its even possible.

just need a bit of re-assurance before i spend $180 on antennas

i went and bought 3 of those antennas and it did not work.

laptop could not see any connections available at all.

so does anyone have a suggestion for a very good wireless router ?