There is a difference between really really good, and high end... But, to the human ear, that is likely going to equate to less than 5% of an audible difference if we were to throw a percentage at it.
Sure, Meridian DSP-8000 speakers DO sound better than B&W Nautilus speakers, but not typically worth the extra $$$ that must be thrown into them.
This is just the same at every budget. You want to think about what you really want, and how much you are really willing to spend to get it. You do get more, as you spend more, but at every price level, there are better and worse products out there... There are also garbage products that do nothing at all to help the quality of your system in any way.
Companies like Denon are very good broad scope manufacturers. They don't make the cheapest of the cheap as Onkyo, or Sony might, but they also aren't really known as making the absolute best of the Best, such as a McIntosh, or Meridian (etc.). Denon is simply a very good mid-level company, which makes them very good for 90%+ of the market wanting good stuff.
Similarly, you have Pioneer, and Yamaha who fit that area as well.
Speakers run the gammut from garbage to great at most price points, so you have to find where your budget is, then do your homework.
Can you spend ten grand? Sure! Easily.
Is it worth it? Absolutely!
Do you have ten grand to spend?
That's the question that nobody can answer but you.
Do you need to spend ten grand to get GOOD audio?
Not at all! If you've done car audio, you know this is true... But, the less you have to spend, the more you typically want to do homework and know what you are buying. There's lots of very good product out there, but there's also a fair bit of crap which should be avoided as overpriced for the value you get.