I had 601's for rears and quickly took them back and got the 602's. I now have the 602's for front mains and rear surrounds. The have more head room (or more dynamic) and better bass responce than the 601's imho.
If you have a good sub and you use your system for home theater much more than music then the 601's may be suitable and cost saving for you - then of course it depends what volume levels you like.