Some info for the interested geeks out there
In a ported (or vented) box, the air mass in the port/vent is effectively isolated from the air in the rest of the enclosure, except for the inside opening of the port/vent tube. This air has mass and inertia, so has its own resonant frequency, which can largely be tuned independantly of the enclosure.
At high frequencies, the inertia of the air in the port is too high for it to respond to the air mass in the enclosure, so it behaves like a sealed box.
At the resonant frequency, the air mass in the port reacts against the air in the enclosure, and vibrates out of phase with it. This results in the air in the port being in phase with the front of the speaker driver, thus increasing output. This also means that the movement of the bass cone is greatly damped at this frequency (as the air in the box is 'bouncing' against the out of phase port air mass). This is why the cone can appear to not move at all, but with loads of air movement happening in the port. I remember seeing a great video of ported box putting out a candle flame!
At frequencies below the port tuning, the port air mass has insufficient inertia to bounce back, and so the rear pressure wave from the bass driver leaks from the port, out of phase with the wave created from the front of the driver, thus canceling out the bass.
For this reason, a ported system will exhibit more bass around the tuning frequency, but will then typically have a fourth order roll off (24dB/octave). A sealed system won't gain the extra bass, but won't suffer from the canceling effect, thus exhibits a second order roll off (12dB/octave).
This can mean you actually get more very low bass on a sealed system (as the roll off slope is shallower). However, it's likely this bass is so low (in both frequency and amplitude) that it wouldn't be much use to you (too quiet to be heard, and below the frequencies of the recording you're playing).
Stuffing (or sealing) a ported system shouldn't cause any problems, but unless there was a very good reason, I'd usually avoid doing it unless the manufacturer had specifically provided instructions to do so (a ported system isn't just a sealed system with hole).
There. That should've bored everyone to tears!