[clive milne]

A couple of things that haven't been mentioned yet...
Arguably, the component that has the single biggest impact on sound reproduction is the speakers themselves.
A close second would be the acoustics of the environment they are placed in.
I would probably put signal processing/management third - digital active crossovers with RTA to set eq, crossover points, time and phase alignment should be considered long before throwing silly amounts of money at cables or amplifiers. If you haven't at least bi-wired your mains, you shouldn't be spending money on monster cable.
Don't discount high end pro-sound equipment as an option. It is invariably built to a much higher standard with far better performance than equivalent domestic hi-fi gear for a given price point. The caveat being that knowing what to look for in this field is a skill in itself.
And lastly...The very best use of the time and money you have available to devote to this endeavour is to learn about acoustics / speaker design and build a sound system to suit your specific situation, budget and tastes.

c

And for what it's worth, my background includes designing, building and operating (hi-fi quality level) sound systems for commercial events with up to 20,000 people.