Hi Vekin,
If you find it extremely mild (as in not very piquent), I suggest you try adding more chilli powder or maybe fresh chillis. 3-4 tsp is a reasonable quantity of chilli powder (for one) so you must be using very mild chilli powder?
Yes, if you find it bland, I suggest you add more curry powder (maybe another teaspoon) as you suggest.
As a point of interest, I think it is generally much better to use a mild curry powder and add your own chilli powder (and/or fresh chillies) to make the curry as hot as you wish. Mild curry powder generally has a better range and balance of spices in than medium or hot curry powder.
Make sure you cook both sufficiently well, but without burning them, (maybe make a paste, with water, to avoid burning them, and cook until the water has evaporated)
Maybe try adding a teaspoon (or so) of dried fenugreek leaves too (add just before the first ladle of curry base).
Please let us know how you get on the next time around
