Streamline Upgrade; Old NightHawk to New NightHawk

Unless you're paying for multigig speeds, the RS100 isn't that much of an upgrade. If it was me and I was looking for upgrade options while retaining the ability to transition between systems? 
I'd move to a open source setup like opnsense. 

You'd simply build a cheap router without wifi and use the current router as an access point. I picked up a cheap Intel N150 with 12g of ram and 2x multigig ports all for around $100. It runs as my router and then I just use a mesh system for my wireless in AP mode. Much more secure. Is upgradable, has backup options that can be transferred over, better security, built in DNS blocking, etc. Much better system.