A true dual set up shouldn't cost you 1k, if it does find a new shop!!! And the Hemi already comes with hi-flow cats so it'd be a waste replacing them. I've done so much research on the hemi and how mods will improve it. Sure headers, aftermarket hi-flow cats true dual set up will be sick but without replacing the headers no sense on replacing the cats. Best thing to do is go from cat back true dual like I did. I got a dual in dual out muffler for back pressure and scavenging to help get rid of rasp and it sounded great. I also had the Intune which I used the canned tunes and modified the tune myself, I changed shift point on 1-2 to hold the gear a tad longer pushed redline to 5900 which is right before the numbers drop off in the hemi. Then I changed the throttle boast to 17% which takes the delay off when you hit the throttle. I had stock TB, but an upgrade is always nice.
As for the intake mod, super easy but definitely effective, let me know if you need any pointers on this