Bought a House With Built In Speakers [Audio Newbie]

[XXF]

So I bought my first house and the entertaining area has built in wired speakers. The speakers have basic red/black wires that run to a closet and there is an RCA male to male that runs from the entertainment center to the same closet. There are 6 built in speakers and one wire labeled "Center" that has corresponding red/black wires at the entertainment center.

This where I start trying to fill in some ignorance gaps, I think what I need to do next is twofold:

First, I need to get an audio receiver, hook up the positives and negatives and plug in the RCAs to the TV and receiver.

Second, I need a center channel speaker.

So from there... I start to have questions. I admit that I'm a little intimidated by the receivers. They seem to have a lot of inputs and outputs and I've never fiddled around with any audio equipment before, so to start on some questions:

1. Are these the only necessary inputs and outputs I need for my situation?

2. If they are, can you describe the advantage of getting this one (pictured) over this one, which seems to be a budget one?

2a. If you think I'm heading down the wrong path regarding receivers please let me know.

3. When it comes to getting a center channel speaker to go with my center channel wire what should I be looking for? Is something like this or this the right thing? They don't show their jacks on the back so I have ignorance driven paranoia about this.

3a. I'm open to center channel speaker recommendations if people have them.

4. There seem to be 5 jacks that the RCA cable can be plugged into my TV labeled "Y", "Pb", "Pr", "L", "R". Is one of these better than the others? Is it a problem that there's only one RCA wire running TV to receiver?

I hope my ignorance hasn't physically pained too many friendly audiophiles and some fine folks out there on Toms are willing to help me get my feet wet in this.

Thanks (so, so much) in advance!

 

[dudio]

1) I like Onkyo much better than Sony, and I suspect that receiver will do it, except that you say you have 6 speakers plus a center (and a male to male RCA to go to a sub woofer that is longer there. Therefore you have a 7.1 audio system or a 5.1 with a seperate pair in anther area meant for Zone 2.
Are all 6 speakers plus the center channel located in the same entertainment zone, or just 4 and a center?
2) Onkyo
3) Not a big fan of Polk (tho I have a 12" subwoofer by them). The 2nd center speaker you linked is nice, but also depends on what kind of quality your existing speakers are now. Can you see make and model?
4) The Pb Pr blah blah is for video (Component).. somewhat older 1080p compared to your HDMI inputs. The 2 yellow inputs are your lowest quality inputs.