Hey corelli,
From what I understand the Gaia isolation footer drain the vibrational energy from the speakers, diminishing distortion. They don't change the sound signature of the DI's at all, they clean things up allowing their sound to emerge more clearly. It's one of those subtleties that make for a significant improvement. I'm not sure if it's on the level of a crossover upgrade as I've never done one, but it was a very surprising and pleasant improvement.
Adding subs to the DI's/SE's is intriguing. I don't find myself wishing for more bass with the DI's, it would be interesting hearing what a pair of subs might provide. Maybe a pair of Tekton Brisance?
My sentiments exactly David. It's been a pleasure sharing my joy of music and audio with everyone here.....especially in such a cordial and welcoming manner.
Happy Holidays everyone.