Originally Posted by tom2112

Short answer:
About $1100 gets you 400+ crank hp.

Long answer:
The SRT-6 was advertised at 330 crank hp, but actually has 350 crank hp - bone stock. It was a Chrysler / Mercedes marketing thing.

Most aftermarket or even DIY cold air intakes will get you about 25 whp (about 30 crank hp). There's a bunch of them available, but most perform so similar, its largely a matter of personal preference. The NeedsWings CAI costs $450.

A supercharger pulley will get you another 35 whp (about 40 crank hp). The only supercharger pulley available is from Code3 and costs $650. You can also go with a larger crank pulley. There are a couple manufacturers, and they generally run about $1000. The 178mm crank pulley is supposed to be power equivalent to the Code3 SC pulley. Larger crank pulleys are also available.

A custom ECU tune varies on how much power it will get you. Some folks here have seen increases of 20 whp (about 24 crank hp). A custom ECU tune can cost from $500 on up, depending on where you get it.

Soon to be available are aftermarket intake plenums. The prototypes made 37 additional whp (about 44 crank hp). They should be available soon from NeedWings. Pricing hasn't been announced yet, but will probably be close to $1000.

So if you went with all of that, you'd have approximately:
Stock:__350
CAI:____+30
Pulley:_+40
ECU:____+24
Plenums:+44
===========
Total:__488 crank hp (about 390 whp) for $2600

Of course, there's a few other things you should do to keep all that power from being sapped by heat. Such as a new coolant pump ($150), separate your engine coolant from the intake coolant (custom), larger heat enchanger (may or may not actually help), phenolic spacers (about $100), and perhaps modding the electronics controlling the coolant pump and fans.

And there's more radical - or should I say less popular - mods such as meth or alcohol injection, conversion to E85 fuel, and many others.