The 350 is a better bang for the buck than the DSP3100, I did an A/B/C with the 350v3, the DSP3100 and the 350v2 and I would say the 350v3 has a much better impact for movies, for music you could do either the 350v3 or the DSP3100, once you have felt the realism of a nice sub for movies there is no going back.
And since I am such a huge fan of the M80s I would say, if you can, get them as well. The 60 are a very good speaker but the 80s are that much better. Just as Fred mentioned if the 60's are all you can swing to get the 350 then by all means stick with the 60s and 350, you will not be disappointed.
