I run a JBL system, ex-recording studio near-field monitors of more than 20 years old and are still in almost perfect condition (with the exception of a new voice coil on one 12" driver). The front 3 are huge and the rear surrounds are JBL's larger bookshelf models. Plus I also run a pair of tiny 2-way Wharfedale bricks for height and a a pair of 'home grown' bookshelf's for centre back. I removed the front wides after a few weeks of use as being of little use (at this stage), space consuming and they were ugly.
I have been running this setup for about 12 years now in my dedicated 21x15 theatre (now with a 136" widescreen) and have tried/tested/used almost every cable type I could get my hands on (my son is a high-end AV installer) and neither he nor could ever tell the difference between a squillion dollar Monster cable, the cheap twisted pair I use for everything, or even 2-pair telephone wire (it was a test so don't faint).
There are certainly scientific tests that show the inductance & capacitance between cable pairs, over long distances, makes a small difference, on test instruments. But we have never been able to actually prove, beyond perceptions, that there is any discernible audible difference between any of them. So at the bottom of any list of gear improvement needs are the cables. The only factor one needs to be considerate of is cable length. Resistance of the wire, over distance, is the biggest factor effecting performance and this is really just a power limiting issue.
So my bottom line is - speakers must be first, then you will know how much grunt you require to drive them, testing this in your room, (after an Audyssey setup), not according to a salesman or test paper. That means the amp(s) is next. Then comes the screen, furniture and then room treatment, (in that order), and of course you sound-proofed the place before you started moving anything in.