RAM sub box
If you want subs, gonna have to give up your back under seat storage. Personally I think the FoxBox is the best, it has the most air volume I've ever seen for a RAM however this box also covers up the cup holders and you have to put a spacer under the back seat. But there is an option for like $16 and you can add cup holders at the same spot on top of the box.
If you don't want to lose the cupholders then the Q-box Qbomb QC would be my next choice. This box is also ported so should sound very nice. I currently have the regular Q-box 2 10" kickers and its not the best. My dad's friend has the same subs as me with a proper box in his trunk and it sounds much better with better lows.
The reason I suggest the Qbomb QC is if you compare the pictures of the two (QBDODGEQC210 vs what I have the DODGE10 4DOOR) the Qbomb has more volume as it also fits up under the backrest. and its also ported.
The air volume for the QC is .9 cu.ft where as the regular one has only .65 cu.ft.
The kickers i have suggest at least 1 cu.ft. Which suggests why my system doesn't sound all that great but it rattled the rear view mirror off before I tightened it up lol.
I will try to post pics in a bit.
For the subs themselves, I suggest Skar audio. They are the greatest I've ever seen and heard. I currently have one of their amps, and when I get some change I'll be upgrading the box and subs.
2003 Ram 1500 4.7
Flowmaster 40 series single in dual out, Spectre air filter