He didn't ask about gains, only sound. Now that the "don't waste your time on a V6" V8 owners have spoken, I'll try and answer your question as
hunttriumph1500 did. With just the mufflers, and stock resonators, you will not get the same sound as the full system. The S-Type (and ATAK) have their own, matched resonators that also contribute to the sound. I can't say what kind of change you'll get with just the mufflers. If you did just the mufflers and the exhaust shop can make J-Pipes for the back, that would be closer to the full Borla system
I have the Solo Performance Exhaust, it's considerably less and sound great IMHO
Exhaust Kit Details This kit includes muffler, exhaust pipes, clamps and all necessary hardware. This kit includes dual cat back exhaust, your choice of tips and J-Pipes. Application Challenger SXT V6 ( 2015-Present )
shop-solo-performance.com
Solo Performance Exhaust Installed After listening to countless exhaust videos ;) I had decided on the Solo exhaust. It arrived Wednesday. Unboxing: Boxed goodness Muffler Assy and Tips Left and Right Tips Tailpipes and J Pipes Freebies :) Had them installed today: OEM Exhaust...
www.challengertalk.com
I got the quad round tips as well which look great
Both Borla systems come with no tips, you retain the stock Bright Tips on the fascia
The next higher priced than Solo is the Flowmaster American Thunder
Flowmaster's American Thunder Cat-back exhaust system for the 2015-2022 Dodge Challenger SXT is perfect for the person looking for a moderate exterior sound level while maintaining a mild interior sound with all of the performance benefits that you would expect from Flowmaster. This bolt-on...
www.holley.com
Then there is RIPP
RIPP High Performance Exhaust System When it comes to the Challenger exhaust system RIPP spared no expense. This hand crafted exhaust utilizes complete T304 stainless steel inside and out. Stainless welds are carefully placed on all components. During research and development we've experimented...
rippmods.com
Both just use stock tips. There are others, but I've not seen members who mention using them
A Guy