While the extra info is nice to have there is no router made that can break the rules or limits placed on power.
This means that to solve this we use the usual solution of a second WAP. Move the current ADSL+WiFi router to one area and let the other get served with another WAP.
Only your newer network will search for a better router or hope such will cure coverage issues. This is one of those well done areas but I understand you may be new to WiFi networking. here's a primer for you on the issue.
http://now.avg.com/boost-home-wi-fi-signal-strength-part-1/
Heatmapper can help you put your existing router in a good spot for one area and then the second WAP to cover the other area.
Bob
HI , Currently I live in a 2000 sq feet house .I have uploaded the floor plan in the gien link
http://s238.photobucket.com/user/8aum/media/router%20location.jpg.html?sort=3&o=0
I own a TP link TD W8961ND modem+router and get average signal strength in ground floor.I do not get any signal on the first floor on the other end of house even though i tried placing the router on the central location in the ground floor. Kindly suggest me a good router+mode for this purpose.I do not want to use range extender. my udget is 50-100$. (Upto Rs 8000)
Thanks.

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