Currently i have 10 speaker 2 subwoofer sound system but it uses the black lear amp under the seat its not harmon. my subwoofers on have an amp on the back of them. is it possible to just direct swap to the harmon amp to get more power and hopefully improve sound quality if it even will?

 

According to these wiring diagrams, the connectors are the same. I f this is the case, then it should work although I'd only try it if you get a really good deal (like free) on the amp. With old speakers you my not see much improvement. 2002 Land Rover Discovery with Harmon Kardon Wiring Information, 2002 Land Rover Discovery with Alpine Wiring Information

 

I used to install car stereos and a lot of people were very disappointed by the end result of just swapping in a bigger amp. It's not usually more power that's needed to create better sound, it's new/better speakers. Speakers, especially in cars, get dried out, dirty, torn, vibrated and heated/cooled all day, every day. They start to give out after a while. If it were me I'd replace a few speakers first and see how they sound with the stock amp, you might be surprised.

 

+1 or 2

 

Have you replaced the head unit yet? I kept mine for awhile and started by updating a few of my speakers with some Rockford Fosgates. I went with their cheaper line and it was a small improvement.

Then I finally got tired of not having Bluetooth and hands free calling in my 04, so I just installed a new pioneer head unit and wow what a difference.

I haven't upgraded any of the speakers in my 99, but I put a jvc arsenal head unit in it and it also has very great sound.

 

This isn't my ad, but I ran across it today while surfing Craigslist. Thought it might apply on this thread.

Pretty good price for a Brand New Amp!
new Harman Kardon amp for Land Rover