Your ears may not be deceiving you. Speaker wire is sized (the gauge) based upon the speaker load (4, 6, or 8 ohm) and the distance from the amp to the speaker. Longer runs need larger diameter wire. If your previous wire was too small then, yes, you would probably hear a difference.

What distances are you running, what are your speakers rated, and what gauge wire did you use before? It is also possible that your previous wire from Lowes had broken strands that effectively lowered its gauge.

Regardless, nice to hear your system sounds better with such a modest "tweak" and you received unsolicited approval from your wife!