Speaking completely intuitively, 3 * 600W HID lights would be considered "ample" for your grow space, I believe. (btw I say "3 * 600W HID lights" because 600W lights produce more lumens per watt than 1000W HID lights... Fact.)
Since I'm a nerd, I could help you out with the calc if you want?
, you mean that you have a 2m x 3.5m floorspace and 2m of height to work with. Is that correct?
If so, you'll have an area of 7m^2.
From some quick googling, I see that one wants about 50 of power per square foot (no bloody square meter threads anywhere to work from, so a conversion is unfortunately in order...). Since 1 square foot is equal to 0.092903m, that means that your 7m^2 grow area is equal to a 75.3474 square foot grow area.
75.3474 * 50 = 3767.37W needed.
Intuitively, I was wrong...
Like I said, I just did a quick google search to see what a respectable W/square foot would be. Perhaps 50W/sqft is an unrealistic aim. But I also must emphasise that a 7m^2 grow area is very large, and you could potentially have quite a few plants in there. How many plants are you looking to grow?