First, you need to audition the Wilson's seriously. While many might judge the Wilson's to be "better," there are some people who do not like the Wilson sound. Best to verify for yourself.
If you find you like the Wilsons, then How Much better do they sound to you? If it's a big difference, then they would be worth paying up for. Otherwise, it becomes more of a value judgment on your part.
Another issue is how committed are you to improving your system? Many of us have gone through numerous upgrade cycles where all of our equipment is gradually replaced with "better" units. If you think you will eventually upgrade from your Marantz and Parasound, then probably the Wilson' might be the better choice, assuming you like their sound.
If you find you like the Wilsons, then How Much better do they sound to you? If it's a big difference, then they would be worth paying up for. Otherwise, it becomes more of a value judgment on your part.
Another issue is how committed are you to improving your system? Many of us have gone through numerous upgrade cycles where all of our equipment is gradually replaced with "better" units. If you think you will eventually upgrade from your Marantz and Parasound, then probably the Wilson' might be the better choice, assuming you like their sound.