When my cd deck is on for about 30 minutes, I can feel the cd plate heating up along with the CD deck and its slot. I was wondering if this is normal?

 

That depends on how much heat your talking about, any amps heat sink will get warm, even real warm, however if it is getting hot, you have a problem.

What is the MM&Y of your car?

What is the make and model numbers of the HU and anything else in the audio system?

Over-heating of amps heat sink can be caused by a few things...

Restricted air flow.
Over-driving the amp.
Poor current supply.
Poor amp ground.
A low impedance, "load" on the audio output.
A short to ground or other audio output lead.

If you are using a "high powered" HU to drive 4 speakers, and the HU is connected to the stock radio harness, directly or with an adapter harness, it is a good bet that it is poor current supply and a poor ground, [actually all part of a current supply problem], the stock wiring can not "deliver" the current the HUs internal amp needs to produce it's rated RMS output, so the amp starts clipping, [distorting] producing heat at the audio outputs, [ICs mounted to the heat sinks] the output from the amp, [to the speaker] changes from AC current to DC current, and that's bad for the speakers.

If the above is the problem, the fix is to run a fused 12ga-10ga power lead directly from the batt. to behind the HU, connect the HUs constant power, [yellow] to the lead, just like powering an off board amp, don't forget to cap off the stock constant power you are no longer using.

The HUs black ground lead can go the the stock radio harness ground, but you will need to add a HU chassis to car chassis ground, on most Honda/Acura that chassis to chassis ground is made when a metal "L" bracket is used for the HUs back brace, from HU to stock rear support.
If HU is in ISO, using screw holes in sides of HU, chassis to chassis ground is completed when housing is mounted. 94

 

1995 Honda Accord 2dr. I noticed that my volume sounds actually "lower" now than before. Around Volume 5, it still seems like you cannot hear anything.. just a little bit. Volume 10 would be a little more. But Volume 15 is where I put it now and I can hear things better, so I'm not sure if its what you mentioned about poor grounding. I could've sworn before at Volume 5, it sounded fine with my other HU.

 

What is the make and model numbers of the audio equipment? 94