Pioneer sx-255r can i connect 6 - 8 ohms

yes you can

You need to hook it up to another analog input other than the phono input. The record player has a built in preamp, and the receiver's phono input has a separate preamp for non-amplified players. You cannot have the two hooked to each other.

You should have an headset jack on the computer. This is the easy way I have found to play music on other systems.

The only relevant speaker spec is the impedance. As you probably realize the Pioneer SX-255R recommends 8 - 16 ohm speakers.

Four ohms is on the hairy edge of too low. You could certainly try it but if any strain or excessive volume is used you could see something go poof!

The low end of 120Hz says don't push the bass to them.

Yes, but it depends on your laptop hardware and software. We'd need to know a lot more about that side.

Just to be sure we are talking the same unit I have included the link to the user manual for SX-255R
http://www.pioneernz.co.nz/Site/Pronto/Files/user_manuals/SX255R%20USER%20MANUAL.PDF

Suggestions
1. have you tried to press the Muting button on the remote unit.
(item 11 remote unit diagram)? does it make any diffrence - what if the button is stuck?

2. Have you tried to play the Tuner radio - what happens then? do you still get Muting.

3. You mentioned something about speaker wire coming out.
I understand that Pioneer receivers shut off if any of the speakers is faulty, ie, correct impedance is not showing at the speaker input point.
Usually the newer units give an "overload" message. It is possible this could be happening and the SX-255R gives the "muting" message instead. Some people have reported very minute shorts where strands of the speaker wire touch the body and it causes "overload".

One way to check is to remove speakers wires one by one and see if the "muting" goes away. Then you can check the offending speaker if that is what is happening.

Good luck
Please do drop a comment to say how you progressed.

One pair goes to bigger speaker (woofer) and other pair for smaller speakers in box, to get full frequency response, you need to hook both cables.

Looks like a scanned version of the user manual is available on
http://www.pioneernz.co.nz/Site/Pronto/Files/user_manuals/SX255R%20USER%20MANUAL.PDF

good luck to those who have been on this post

Power source harmonics. Or its power supply regulation. Check also if input line is touching something.

If the amplifier has a normal AUX selection the ipod can be connected using a standard single AUX cable.