Which receivershould i get?

All of those prices listed sound great if the units work.

What you need to do is study the specs of each, they are listed online.

Check product reviews online as well.

Check ebay auctions (open and closed) for what these sell for and

general popularity or scarceness.

When going to look at one, have them power it on with speakers to

check functionality, check all controls, look for scratchiness, static, frozen controls.

This can sometimes be hard to do if the owner has it stored outside in the garage in a box.

If need be, bring your own speakers, cables and peripheral devices,

and insist that it be hooked up and powered on before buying.

You would not buy a car without taking a test drive, right?

I looked into two of these that you had listed.

I am no expert regarding these models you had picked.

The Marantz seems to be an early 5.1 receiver, not high end and rather scarce.

I would probably steer clear of it.

On the other hand, the Kenwood VR-405 seems to be well built,

popular in it's time, has a good set of control functions, is powerful and reliable.

With 400 watts total output (80W X 5 CH), I would not stack anything on top.

That well ventilated case top needs to breathe. That is, let out the heat.

It also normally sells for quite a bit more than the price you listed.

Do your homework grasshopper.

It is you that will need to live with (and hopefully enjoy) your choice.

Looked into the Sony as well.

Average used selling price is ~$150. (new in 2001, price was ~$500)

Abundant features, good power, 500 watts total (100W X 5CH)

Mixed reviews on reliability, seems that most like the sound and controlability.

As old and as complicated as this unit is, something is bound to break sooner or later.

Buyer beware. But hey, for that price you cant go wrong if it grenades sometime in the near future.

You roll the dice with used gear, you takes your chances.

If it were me, I'd find the tech manual online and fix the damn thing when that time comes.

Only problem is that finding some of the parts can be tricky.

Look at the Onkyos you posted, messed up soft touch buttons.

Good luck ever finding those again. One would have to buy a donor unit for parts to fix it.

Or find a repair shop that has a direct pipeline to source Onkyo parts. (if they are still out there)

Regarding your last post about subs, here again I am no expert

and I cannot vouch for the sound or reliability of the units you posted.

They all seem good for the price but without hearing them, who knows?

Do the homework, research them online and check the auction sites.

Since you are not buying a complete system that is sold by one manufacturer,

matching components can be tricky.

What you need to know is how these will connect up to your main amp.

What you listed  are all "powered" or "active" sub-woofers, meaning they have their own

built-in amplifiers, therefore only requiring a line level or low power preamp signal from

your receiver. If they were "passive" subs, they would need the full wattage output

for that channel from your receiver instead. You will need to check if your receiver has

preamp output terminals for the sub channel. This is prefered because it takes less

power from the main amp in the receiver, thus allowing it to run cooler.

Less stress = less mess.

Another thing to look for is if the sub takes a direct signal from the receiver

or if it is set up for a "pass through" signal that would subsequently feed the other speakers.

Some newer multi-channel integrated systems employ this method of signal distribution. 

Here is a link explaining some of the above:

http://hometheater.about.com/od/loudspeakerssubwoofers/qt/Passive-Subwoofers-Vs-Powered-Subwoofers.htm

Yes it does have an output for a powered sub, I checked.

The pdf download for the user manual is available online.

Just google Kenwood VR-405 manual.