I wouldn't bother with a $6k supercharger unless you've got another $2-$3k for a Transmission that can handle the power.
Guys are frying the stock 545RFE with just an extra 40-50HP with minor bolt-on's already. MGH's Twin Turbo'd 4G Hemi roasted his trans within 1000 miles.
Headers help exhaust flow from the cylinder heads.
The collector is further down the line than having all 4 of the cylinder exhaust ports all fighting
for the same constrictive escape route in the small volume stock cast iron manifold.
Stock Hemi exhaust manifold:
A Short Tube Header ( like JBA) provides a better than stock flow, maintains factory cats that are already fairly high flow in a 4G Hemi.
They go for about about $400, and $150 more for Ceramic Coated.(+/- 15 HP gain)
Long Tube Headers (ARH) provide the most power/torque (about +/- 30HP) if you have the proper supporting mods. The tubes are much longer than the shorties.
They also replace the factor cats with a higher flow cat and move them further down the pipeline and provide an un-restrictive Y pipe where the two sides combine just before the muffler.
Prices start at $1600, and it's another $250-$300 for Ceramic Coating ...not required but good for better heat reduction under hood, lasts longer, looks better.
If you dont have $2k to spend on Ceramic Caoted LT's, You can go with a Shorty Header, keep your factory cats, and get a 10778 Magnaflow Y pipe ($27)
That's the route I'm going with very shortly parts arriving within the couple weeks...and I'm already a 13 second (Heavier 4x4) 4G Ram
My next run will be with JBA Shorties, 85mm Fastman TB, Y pipe and probably an Edge 2800 Stall TQ Converter to get me out of the hole quicker.
Magnaflow Y pipe:
This is what the stock squash bent Y pipe looks like for reference: