That Kenwood amp will do nicely
Good choice. The RMS value is what power the amp is capable of producing. You can use any amp on any speaker as long as the speakers can handle what the amps can give.
That is 2 Channel, so what you do is follow the instructions given and use it bridged, i.e. it could be that you use the left channel positive and the right channel negative to achieve this. It will show you on the amp.
To lower the ohms to 2, you will need to connect one positive of one sub to the negative of the other sub, thus leaving you with one positive, and one negative at each end. So the power goes from the amp (+)into sub1(+), then sub1 (-) into sub2 (+) and sub2 (-) back to the amp (-). This is what you call "Series" (i'll do another diagram for this)
Parcel shelf (rear deck) mounted speaker are what you would class as rear speakers. Basically, i need to know if they stick into your boot space especially when its closed, thus reducing the available height, thats all. All these things have to be considered when making a box, so you know its gonna fit.