How long have you been training? Begginers can gain muscle while losing fat eaisly up to a point. After that your progress will stall if you don't make the decision to do one or the other.
You can be lean while gaining muscle as long as your diet is in check. As long as you are taking in a surplus of calories you will not lose muscle as long as you continue to lift with the same or greater intensity. You may gain some fat in the process. How much fat you gain is a function of how much you eat and how quickly you want to put on muscle. It is very hard (i.e. takes a very long time) to gain a lot of muscle without putting on some fat.
If you want to be a powerlifter you will need to eat and lift hard without worrying too much about body fat. Pick a goal and stick to the plan that will get you there. If it is really important to be at 10-12% body fat, then diet until you get there. You will lose some muscle in the process since you are not that big to begin with. Once you are there, then pick a goal and go balls-out to get there (i.e. weigh 200+ lbs and bench 100+ more lbs or whatever). You will gain some fat back in the process, but it will be much easier at that point to cut to remove it, due to your increased muscle.
Personally, I don't think 15% is that high - I would start the bulk now without looking back.
i am a powerlifter, and my focus is on shoulder press and benchpress.
so my main focus is to get stronger, but i also want a decent amount of muscles. and a relativly low bodyfat level so that i'll show. a six pack isn't really that important for me( personally i think that girls like buff guys a little more than those skinny twigs)
could you please define how a bulking diet would be? like protein, carb and calorie goal.
It varies from person to person how much weight you can gain, and how fast, while losing/maintaining bodyfat%. It also depends on how close to ideal your diet is. If you were previously eating twinkies and donuts all day and lifting, then reduce calorie intake while increasing quality of food (changing to veggies, lots of meat and eggs), you can lose/maintain/gain weight while losing bodyfat%, but that only works up to a certain point...over time it gets harder and harder to keep gaining muscle at all, let along while getting leaner in the process. Find out your own limits. Then break through them, no matter what it takes. Sheer determination often overcomes "genetic limits".
What do you mean when you say you are a power lifter? What do your lifts look like? What is your main goal? Most power lifters could care less about how they look, their goals are usually to gain strength in the core lifts. Getting lean and gaining strength are two opposite goals. If you are very new to weight training then it is possible to do this, but not for very long, and especially if you don't have a perfect diet.