in a small space like yours, based on your door size I'd guess you have about 10' x 12' give or take. Its really difficult to do any kind of serious suggestion without knowing the exact measurements, the contour of the ceiling, what other "stuff" will be in the room, and what the floor is going to be.
Hardwoods are going to reflect more of everything than carpet, which will absorb higher frequencies. Without a doubt in a rectangular room this size, you're going to get killed on bass frequencies (standing waves), so you're going to definately need to treat the corners as I've illustrated below. Its possible, you'll have to put some additional absorbers on the side walls, and if you want my opinion I'd "feather them" so the angle slightly off the wall, say, a 5 degree angle (closer to the wall towards the bottom of the diagram, further from the wall towards the top of the diagram). This way, you don't have smooth surfaces on the two side walls for standing waves to bounce off. Not only will you absorb the bass frequencies, but you'll also reflect some of it in strange directions thus breaking the standing waves even further. I did this in a very small bedroom studio years ago and it worked well. I used heavy blankets in a wooden frame, but with 409 fiberglass being reasonably available, you should make your absorbers out of that material instead. You'll find "pretty" products like Auralex absorb high frequencies, which you might need some of, but tame the bass first and listen to how you like your room first, then spend a few dollars on foam.
