In my opinion, no.

Unless you have a fair amount more power and intake mods to complement it, an x-pipe will be of no benefit. One possible negative is that x-pipes produce a "higher tone" than h-pipes.

Disclaimer: I have an x-pipe on my Marauder as part of a system with Cobra manifolds and high-flow cats that I bought from Dennis Reinhart many years ago, but it also has a Trilogy Eaton supercharger and makes significantly more power than stock. I always thought my ex's Marauder with an h-pipe and Flowmaster 50s sounded more like a muscle car.
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'03 Mercury Marauder (The Blackbird)
Trilogy Motorsports supercharged #61
Too many mods to list / Driveway Queen

'04 Grand Marquis LS Limited Edition (Spruce Green)
Daily Driver (Thanks, Adam!)

'00 Grand Marquis GS (Silver)
Rotted frame and broken transmission crossmember
Being resurrected...slowly.