the problem that i have experienced with single carb is that its a lil bit lazy at high end...if you have driven your car above 5000rpm then you'll understand what i am on about. I have experienced the similar problem with many single carb hondas..beyond 5000rpm the revs build up at a very slower speed compaired to a dual carb or a VTEC.
There are people who carryout various mods on single carb but whether they give satisfactory return is somewhat questionabe.. Well ofcourse you'll get a bit more power but you'll also be visiting fuel station more often..
Well according to my knowledge you have 3 options..
1. Go for a dual carb setup- for this finding parts would be a lil bit difficult.youll have to find a dual carb setup with the inlet manifold,Housing which holds the air filter element, the control box which has vacuum valves, the computer and some wire harnesses---this wouldnt cost as much as a VTEC swap
2. Go for a VTEC engine - this would cost you above RS.125,000
3. Collect some money, sell the car and buy a EG VTEC---this is the best option