IMO, your space is going to define what speakers are an upgrade.
I sit about seven feet in front and my speakers, Klipsch RP5000s are less than four feet apart.
I would upgrade them if I didn't feel it would be a waste of money, since the space I have wouldn't let more expensive speakers 'breath.'
I would call my apartment 10x12 and I can't imagine spending a lot of cash on speakers so that I can hear the sound bounce off four walls, five if you include the low ceiling (thankfully I have acoustic on mine!)
Space is a limiting factor for me.