110 to 12V in home car audio

ok, hey im new here, and basically thank god for this site. Through learning things ive read on here i have become facinated with audio/electronics. SO my situation:

I have a 500W 110 (wall plug) to 12V (positive, negative and ground contacts) converter which was used for a car audio system display (in house) at a ford dealership. I am trying to hook a little kenwood KAC-723 amp to my onkyo head unit via a "hi-lo" converter or low frequency crossover so i can hookup an extra sub i have laying around and use it to add some depth to my stereo.

My questions:

1. Is this possible at all given the different power sources? Does my HU for my house give out a different power than my crossover can use?

2. How do i need to hook the power from the power converter to the amp? My only personal source said i need to run the positive and negative to the power contact on the amp to complete the circuit, then hook the ground to the ground (obviously).

3. My hi-lo/crossover has a positve, ground and remote terminal. Does that mean i can hook the power from the amp into the X-over, then connect the remote terminals from the X-over to the amp, and leave the ground un-plugged as far as the x-over (the way it was being used inside the car it was taken from) is concerned?

As it stares me in the face everytime i sit at my computer, not working, my current connections with the system are as follows:

Sound signal:

HU>X-over>RCA's into amp

Power:

Power box positive and negative>positive contact in amp

Ground:

Power box ground>amp ground

X-over:

Both left and right positive and negative>positive and negative left and right contacts

X-over power:

Amp power contact>X-over power contact

I hope this made sense, LET'S MAKE THIS WORK!

if I'm correct in what I'm reading, you have a home receiver, a car amp and a 110VAC to 12VDC power supply.

You should be fine just hooking up the power and ground from the amp to the power and ground on the power supply.  Just jump the remote wire to the constant wire so the amp will be on whenever the power supply is on.  If your recevier has RCA outputs for a subwoofer amplifier, you can use those to input the signal to the car amp you've got.  If you don't have outputs, you can use an automotive LOC to get RCA inputs for your amp. 

You should not have to use the ground contacts on the power supply.  Just use the positve and negative terminals.  That's the only correction I can see in your setup.  Just treat the power supply the same way you would a battery, hook up your positives to positive and negatives to negative

hornshockey has it right.

so hook the positive from my power box to the positive on the amp, and hook the negative from the power box to the ground on the amp? and leave the ground out cause its grounded through the negative right?

Using 12volt gear powered from 120V power supplies is never a very brainy idea, unless you are very careful to properly fuse your power supplies.  And as was stated above, 120V/12V power supplies with adequate power capacity for any high-power car audio amplifier are very expensive.  Using a raw battery and a charger is not safe if the battery is lead-acid, and you can easily blow your charger since most of them max out at 20 or 40 amps.

Bottom line is it is safer and cheaper in the long run to use gear designed for the home in the home and use gear designed for the car in the car.