Well to be fair you wont gain or loose power at all, you'rs just shifting it around. But yea, adding teeth to the rear or subtracting to the front will give you your desired effect.
Things to remember:
Subtracting teeth will make the chain bend tighter around the front sprocket, and with current gearing ratios adding one tooth or subtracting one tooth to the front sprocket is close to being equivalent as removing or adding 3 teeth to the rear..
Adding teeth to the rear sprocket will give you less of an effect as the front but its easier to change out.. Depending on the set up you want you may have to lengthen the chain to accomodate the larger diameter sprocket.. It seems as though you can fit a +2 rear sprocket without any chain modification.. The -1/+2 setup is still quite a jump, first gear will be pretty close to useless unless in a parking lot..
The thing with gearing is allows you to explore the grey area in between gears, some people change their gearing so radically it doesnt make sense, you could just click the transmission down a gear and get the same effect.. When we change final drive gearing we are just in that grey area..