How much is that doggy in the window? $129.99, with pre-orders starting today. So, for between $230 and $330 you can have a simple wireless stereo setup. Of course, if you're after sound quality, you should skip the Echo Dots and stick with the Echo Plus, which has been marked down by $50 as of this writing.
There's an absolute trade-off here between sound quality and convenience. Sure, the setup on a traditional stereo system might take a little longer, but you only have to do that once anyhow. Amazon crowed about how good the Echo Dot and Echo Plus sound from the stage, multiple times. Neither of those -- the Dot in particular -- sound amazing, and the company wouldn't have released the Sub if they did. A subwoofer will add bass to music, of course, but it won't fix the Echo line's weak midrange and highs. Those are other problems altogether.
If you'd want to skip the Echo speakers wholesale and grab an Echo Input and a pair of powered bookshelf speakers, it'd be a much better value and you won't be locked into Amazon's streaming ecosystem exclusively, either. Regardless, no matter what Echo setup you choose, it'll still cost less than Google's $400 Home Max speaker.