Besweet can do the downmix automatically (there is no need to divide into 6 channels and merge them manually). The default downmix matrix is also Dolby Surround compatible, so when the 2.0 file is played back with pro-logic decoding you get a centre channel and a (mono) surround channel. The downmixed output is fine, what pittrek means when he talks about poor quality is the result when using BeSweet to encode to AC3. If you need the 2.0 encoding to AC3 you're better off using a commercial encoder if you have access to one, or the open-source encoder Aften. Alternatively you could encode to MP2.