It’s not the cables. Great cables can enhance an existing system.
Two places to look. the first is the Maggie’s placement. They are incredibly sensitive to exact placement. To the 1/4" in toe in. Maybe they got moved
So:
• 3–4 feet from front wall
• Carefully toed
• Properly driven
• In a room large enough
Which brings us to the amp. Has it been serviced? I think it is 20 to 25 years old. It may need serve as @idrachman mentions.

