Can we increase our speed by replacing some other high End DSL modems

Can we increase our speed by replacing some other high End DSL modems with PTCL's original ones i just wondering that if it possible so i'll change my current ptcl modem and also please mention some ADSL modems too

my second question is what setup & equipments do i need to use my dsl internet outside home e.g. street around (I checked some shopping site which are selling wifi boosters can these boosters increase wifi signal)

1. No speed almost remains same, some 5-15Kb/s difference in some cases.

2. I have PTCL WiFi router and i can catch signals in my street also, also there is this Cable Network guy and he is using some Tp-link router and i can also catch his signals inside my home, his shop is in the next street to my house. So i think you don't need any boosters.

You don't need any wifi boosters for wifi in range of almost 200 feets. For details read this http://www.dd-wrt.com/phpBB2/viewtopic.php?t=43810&postdays=0&postorder=asc&start=0&sid=a40a6c6d3787eb6addcb0ffca2046d4d

A different modem might improve you line stats nothing else.