The other speakers are NOT powered. Yes, you will need some sort of amplifier, most typically a receiver. If you were capable of adding an audio out plug from the typical just a few to 15 watts built in amp for audio, the signal would be insufficient to run the external speakers. The TV tuner is your video "receiver."
As to how to connect, visit the very welcome http://www.wirewize.com, which will make it easy for a person like you who may tend to jump to conclusions.
Some fundamentals include the idea that HDMI is a one wire connector which conveys both video & audio.
Now, there are a few alternatives when it comes to wiring the connections. Especially when blessed with plenty of HDMI connectors, some of us prefer to connect the disk player directly to the TV instead of by way of going through the receiver. Typically, TVs may do a better job of processing the signal rather than possibly introduce problems by going through the receiver as another device that may add video "noise" by imperfect processing. From the TV, the audio output signal will be amplified for the speakers (with exception of the self powered sub woofer.)
The audio out of the disk player must be routed through an amplifier. The disk player cannot have wires from it directly to the speaker set. That situation has no amplification for the audio. As an aside, if your amp would be, say a 5.1 configuration, you cannot get 7.1 out of it because, by definition it only has enough amplification channels for 5.1.
I am setting up my video and stereo devices and I got stuck with the decision about what to use to connect the devices together. So, I have 2 questions.
On one side I have the TV with 4 HDMI inputs which pretty much eliminates the need for having the video receiver. I have DVD player and Satellite receiver and the input connections on the TV that I have will allow me to add a couple more devices to it later on.
On the other side I am planning to buy KEF 3005 speakers that have the amplifier inside the sub-woofer and that eliminates the need for having an additional amplifier. However I should be able to transfer both a) 7.1 sound from my DVD player and b) stereo signal from satellite receiver to the speakers.
So, since I do not need neither the Video Receiver not Audio Receiver, are there some kind of devices available that will work like "audio switch" and will have a 7.1 input/output and regular sound inputs as well? Again, "audio switch" without the amplifier.
I could get a regular AV receiver/amplifier but since I have all of it already, that looks like waste of money.
If I connect my DVD player to TV via HDMI, and then connect the speakers through the 7.1 output of the DVD player, will it transfer the sound via both HDMI and 7.1, or will DVD player figure out that the external sound speakers are connected and will not send the sound to HDMI? Or will it send to both which will make me mute the sound on the TV/disable the internal TV speakers? Could it be so that the sound will go through HDMI and will not be sent to 7.1 output?