I have tons of experience with the Hemi... Great Engines.. I run one in my ROck Crawler/Expo truck. Had the stocker that I blew Nitrous through all the time, and then put a Stroker Hemi 6.4L in her, with amazing results. You cant beat the HP/weight ratio on these engine, the engine weighs about 390 pounds, if you get the Hemi from 03-05 it comes EGR free!!!!!! With the use of 2 spark plugs per cylinder. A true Torque monster all the way through the RPM if you let the engine breath correctly. VERY EASY TO WORK ON!!!!!! DOnt waste your money on Programmers, it really is not worth the money, but a free flow exhaust and a good intake cold air does a little on improvement,,, The RFE Tranmissions are bullet proof... On my stoker engine, I installed a Nitrous oxide kit from ZEX that was specifically made for a Hemi, and you can adjust from 50hp to 125hp safely. I kept mine at 75hp and blew tons of NOS through the engine with no issues (just dont hold the button down for longer than about 10 seconds) But it is true Seat of the Pants performance, and the best bang for the buck for the extra horsepower, When it comes online (the Nitrous) it will def. put a smile on your face...
As far as the stock set up goes, I would save your money on the cold air intake and just use the stocker, DEF> open up the exhaust... and the best performance enhancer would be to remove the stock clutch fan, and install the Black Magic electric cooling fans specifically made for the Hemi set up,,,,, You can DEF feel the difference with removing the stock clutched fan, I am willing to bet that it gave me an extra 10 to 12 hp gain, and a little better MPG also..