The Mackies are not the best choice for a 12x12 room. These are performance speakers and sound best when they are "pushing" a little more air. Consider how loud you need to be, and get a system that runs at or "near" peak performance volume most of the time. The fender Passports might be ggod for you, also the Roland V-Drum amps-PM3
(I have 'em & love 'em).
A good budget system would be to use a home stereo amp and get a pair of "better than average" 10" or 12" full range speakers. Lots of manufacturers make a small 2 way box with a 10 and a piezo tweeter - this will be adeguate for home use....and MAYBE put out enough to fill a room of about 50-100 people at a moderate volume.
Let me know how much money you can spend and I'll give you a better choice for your specific situation. I advise that you go stereo - it's so much fuller and exciting, especially with effects like chorus engaged. You can always get another Roland amp too - that's what Scott Yee uses and he's very happy.