Take all your winter coats and hang them from any available hook in the room; Find blankets or comforters and roll 'em in a ball; set 'em on a chair and so forth. The idea is to frustrate standing waves and reflections. This approach is free and it WILL change the sound of the room. Whether enough, or to your liking, who knows. A friend of mine tried it in a bare room with a guitar and his MXL V67 - piled clothes (had a rollaway with down jackets and such) around where the guitar / mic was - and lots of those problems went away.
Are you using an outboard preamp? That can have a big effect on the sound as well. A Blue Tube preamp allows you to dial in "tubeyness" (tube distortion) as well as gain. A DMP3 preamp is very clean, but doesn't seem to have any harshness. Mixing board preamps (Behringer mixer, perhaps?) can be pretty sharp edged unless you have a pricey board.