Circle App Integration with NightHawk - questions

I have a Nighthawk R7800.  I would like to start using the Circle app, but have questions:

• My router doesn't appear to be supported, so I need to buy a newer version - correct?  I hesitate doing this as the one I have works incredibly well.  If I do need to upgrade, what is suggested to do what's outlined below?  My home is 2,500 sq.ft. and we have about 20 devices hooked to it.  I'm also close to neighbors, so wifi traffic can be thick.  
• If I buy a newer version of the Nighthawk, that does support the Circle app, do I then also need to pay for monthy service fee for the BASIC service?  
• Is there anyway for me to upgrade my current router to include the Circle functionality/program inclusion?
• It appears that I can't add the Circle app to anything but my phones and iPad's, but was not able to add it to my Apple Laptops.  Why is that?  Sounds like I need to do that through my router?

I like the Circle service.  I just don't want to pay a monthly fee if I am also going to have to buy a new router.  I would be happier buying a new router, in lieu of an ongoing monthly fee.  

Can someone please give me guidance on the above?

Thank you!

Shumax