Hey, it's hard to say from one system to another. But if all one has is an avr or receiver with a dvd player for a source and basic speakers, it's doubtful one will gain much in the way of benefits.
Over the course of a few years, I put together a 2 channel system consisting of Paradigm Signature S6 speakers, Parasound Halo A21 and P7 and an Oppo 95. If you are patient you can get pretty good deals, and also find like new items used on sites like this one.
With this system, I was actually somewhat disappointed until I started upgrading my generic, basic cables. Part of the problem with upgrading, is there are so many out there promising the moon, it's hard to winnow it down. I asked around on forums and got suggestions that were not that expensive. Morrow Audio and Audioquest type 4 for speaker cables.
Both of the above use solid core conductors, not stranded. Morrow uses solid copper that is plated with silver. The results are quite an improvement, it's like the cables let through more of the music, more detail.
