Wherever you heard that the differences between dacs and interconnects would be "HUGE"...you should stop going there. They've been telling you tales of Bigfoot and the Loch Ness Monster.
The limiting factor in your case (setting aside the room, which may be perfect for your setup, we don't know) is your speakers. There's nothing wrong with Elac speakers - they're great for the money. But at the end of the day, they're $300 speakers. I'm not saying they're bad speakers, not in the least, but encouraging you to swap dacs, or upgrade your interconnects, or playing with coax vs. USB vs. whatever is barking up the wrong tree. Doing those things may affect the system (though I doubt it, as you've discovered), but the sound will still be coming out of $300 speakers.
If you want better sound, put every dollar you can into upgrading your speakers. And if you're emotionally attached to the Elacs, or simply can't afford to upgrade them, then forget about this thread and enjoy the music you have now. Playing with those other things is a waste of your time and money, and frankly I'm surprised I'm the first person on this thread to even mention a speaker upgrade, though I know it's not the question you asked.