on strut bars: they're all pretty much the same, if you think about it. it's a 3/4" thick piece of metal that you attach to your strut towers, and you can get one for $10 off of ebay, not incl. shipping.
i've never heard of pilot strut tower bars, but i'm pretty sure it didn't cost 150. maybe for 2 bars (front and back).

you'd need to give us more information about the computer, is it a VAFC? is it a standalone EMS? OBD I ECU? generally speaking with ECU/Computer mods, the hardware costs money, but don't forget to TUNE your car with those mods, which also costs some money.

DC vs Mugen: there isn't a comparison. Mugen headers outperform DC headers every time. When it comes to honda, never doubt mugen's products--just doubt their crazy prices :P.