Perdy's a funny boy but sure jumped the gun. Supercharger is probably a tad out of the range Lowes was thinking.
Realistically, for 150 HP or very close you have to change your exhaust and bypass that catbox. Do a triple filter intake mod and then Tuneboy performance tune or at least a PCIII tune. All that will run ya $1500 to $2000 USD depending on your exhaust and intake choices. Any exhaust upgrade is good so long as the catbox is removed.
If ya a cheap boy then you can get the TORs with catbypass and factory tune for around $900 but you'll just be in the 130-135 HP range. Pop in an undertank K&N for another $50 and add a couple horsies.
How much you wanting to spend should be the correct question to ask. Lots of options depending on your budget.
Trirocket, I think you're using a different measure of RWHP than most common over here. You should also state your baseline HP as a comparison. I can believe a 20HP jump with just exhaust and tune but I think you'd also need intake mods to get to that 150 mark (I'm assuming a base Rocket is about 120HP).