Can you damage your speakers by plugging bass port vent?

+1 dynamiclinearity. The "ported speakers have slow boomy bass" is a proverbial old wives tale.

@OP, with the K6 being ported through the bottom of the cabinet, I'm not sure that you will find an improvement overall - yes you can reduce the bass extension, but you will change the overall tuning of the loudspeaker and probably not in a good way. Personally, I've never found that plugging the ports in loudspeakers results in  net overall improvement.

You would be better spending some money on some bass trapping and some absorption for the first reflections. Acoustic treatment is cheap and you can still use it when you move somewhere more permanent.

The only way I could get my R11’s to play nice with my F12SE’s was to plug my R11’s two rear facing ports with the KEF supplied foam inserts. The plugs lessen the bass, but don’t seal.
Frequency response changes verified with room correction software. Then used mini DSP on sub to further flatten. Very good results. 

Try a Schiit Loki Mini and turn the bass down.

@ether

no damage for sure but be aware that not all ported speakers are designed to be plugged. Unless your speakers came with plugs originally chances are they are not. It depends on physical properties of the woofer suspension stiffness and travel. In general sealed speakers are looser and have more cone travel and ported speakers tend to be stiffer with less travel. Some are right in the middle and capable of both modes.

Plugging speakers that were not designed for it may restrict the travel of the woofer such that the output will suffer. 

Such was the case with some PSB towers I had.  Too much bass so I plugged the ports but the sound was not good.  See if you can give yours more distance to boundaries if plugging doesn’t sound very good.