I think good electronics (especially source) is as important as a good speaker. When I went from a mid-fi Marantz CD player to an outboard Dac (first an Ack Dac and then an Audio GD Dac 3SE) the improvement was not subtle at all.
I always heard the phrase "garbage in garbage out" but never believed it until then. That said, there are plenty of good options for electronics on the used market. I am also a fan of Audio Gd gear; they offer stupendous quality at mid-fi prices.