@knorpi I believe you’re talking about the Foundation SX and the Foundation XL. I am an authorized Synergistic Research dealer and have both looms on my floor. Also, despite being an SR dealer for the last 18 months, I am an audiophile first and have been using SR cables and accessories for over a decade before being a dealer.
The difference between the Foundation SX and XL are significant. The XL is more transparent/resolving, more tonally dense, faster, and more dynamic. While the Foundation SX cable series is a strong performer in their respective price tiers, the Foundation XL I think annihilates any other cables in their respective price tiers.
I have a lot I can positively say about the XL cable series, even in comparison to some of SR’s other cable lineups, but I don’t want to go there openly on a forum. That said, I’d be happy to answer any more specific questions you might have on synergy within your system on this thread or over DM.