The combined company will be called Sound United and continue to market each brand separately. Apart from speakers and receivers, there's a fair amount of product overlap -- both Denon (via its HEOS brand) and Polk Audio make Sonos-like wireless multi-room speakers, for instance. Denon and Marantz also sell turntables, and virtually all the brands make headphones and earphones.
None of the company's products are what you might call cheap, but Denon and Marantz aren't as expensive as you might remember from their 1970s and '80s heydays. It'll be interesting to see, nonetheless, if the consolidation causes the prices to go down. There's increased interest in old-school Hi-Fi, in part because of the resurgence of vinyl. That said, most new receivers and other audio products need to handle 4K video, Spotify Connect, Bluetooth and other new technology.