Ummm...bass frequencies are the same in a ported set up or sealed. The port just makes the sub extremely efficient at the tuned frequency.
You are going to get vibrations no matter what. I have several buddies who do the whole carputer thing and they have never had an issue with their hard drives failing. I wouldn't worry about it in you cab.
Forgive me for using logic... but if the frequencies are the exact same... then the port wouldnt need to be Tuned. Tune = a set frequency range. If you made the port hole
larger... the sounds would be different.
And yes.. you are going to get vibrations no matter what. However, there is a
HUGE difference in vibrational levels between a pc subwoofer and a powerful
car sub. (or powerful home sub)
A pc sub might only be rated at 15 watts max (though it will be listed
at like 80 watts rms... which means, it will take 80 watts for a short time without
blowing up, but it will sound like crap doing so)
A typical car sub starts around 100 watts, and can be over 800 watts+. The magnetic
driving power is much greater & the air movement is much greater...
thus the vibrational forces are much greater.
I pretty much guarantee that if you mounted a pcs hard drive on top of a car sub box,
and ran windows as normal while it was pounding away... the HD wouldnt last a year.
The HD heads are small as or smaller than a human hair (I believe). Its very susceptible to vibrations... and as gets vibrated enough to scrape the surface of the discs.. it will eventually destroy itself.
As said... a pc sub probably cant do enough damage to be a problem. And again,
may need a port drilled out on the cabinet to actually be able to hear them well
enough.