For $250 that ML theater system is decent, for $500 not so much. Definitely better than the Polks you linked. The receiver seems over-priced and you could likely get much nicer for less money. Do you have a total system budget in mind or are we just dreaming here? What are you hoping to achieve in your media room? What are the room dimensions?
The shakers in the seat will need some form of sub-amp. They do not require much power, so any decent plate amp tucked away would work. You will need to find out the ohm rating of the shakers and power rating, probably 4 ohm and 50 watts, and decide which plate amps to use and the best way to wire them to the plate amp, either series for 12 ohm mono or series/parallel for 6ohm load if you go with a single amp for all 3. Or just connect one amp per shaker. If they are custom theater seats, you might check to see if a plate amp is already installed some where before buying a new one. If there is a plate amp already installed, then you just need to connect an RCA cable from the receiver LFE output to the input on the plate amp and plug it in.
As for the quality of posts here and the degree of knowledge, I have been in the Audio industry for over 25 years and learn something every time I come here. You get what you give. Come with respect and receive knowledge. Come with disdain and expect ridicule.
PS Since you misspelled your screen name, what did you want it to be instead?