The slight reduction of torque to the knees is hardly worth the additional stress put lumbar spine when keeping the knees perfectly in line with the toes at all times. Besides, the OP's knees just barely passed the toes anyway. Big deal.
Using a clean grip is actually much easier and much more stable than using the "X" grip, and it has better carry over to other exercises (e.g. clean, jerk) to boot. All it takes is a little practice and a bit of stretching if necessary.
While it may be true that less weight can be used with ATG squats, it makes no sense at all that using heavier weights going parallel is better for gaining mass.