Obviously, it's your personal decision if you want to "upgrade" to a 7.1 surround system, but I have to agree with J.C. in the previous post. Unless you have a VERY large listening room, a 7.1 system offers no advantage over a good 5.1 system, and in some respects it is worse since the additional channels of sound are matrixed, not discrete. Last, for what it's worth, there are almost no DVD's with 6.1 soundtracks, much less 7.1, and the Hollywood recording engineers have very little intention of moving beyond 5.1. You should read Bryston's newsletters (see the following two links) which contains an interview with one of the top recording engineers in Hollywood for more info on the viability of the 6.1 and 7.1 surround formats.
http://www.bryston.ca/newsletters/55_files/vol5is5.html
http://www.bryston.ca/newsletters/64_files/vol6is4.html
http://www.bryston.ca/newsletters/55_files/vol5is5.html
http://www.bryston.ca/newsletters/64_files/vol6is4.html