So a salvage yard near where I live has the following speakers:

LH Front Alpine
LH Rear Alpine
LH Rear Deck Alpine
RH Front Alpine
RH Rear Alpine
RH Rear Deck Alpine

They're $55 each. Could I have these speakers installed and consider it a good upgrade or would it require more parts (Amp, Sub, etc)

 

Which car is this for? Model? Year? You would do well to get a look at the Jaguar Electronic Parts Catalog (EPC).

FWIW, on the X-Type, you're talking about speakers that would cost 3 to 4 times that dollar amount that you've quoted. Also on the X-Type, the rear-deck speaker IS the sub, and the tweeters are separate from the bass/mid-bass driver.

I expect that you'll also need the amplifier. And I have no idea whether or not these cars are pre-wired for the upgraded parts.

 

Forget the factory Alpine speakers, they don't sound the best & i've been told that after a while the magnet falls off ! the speaker frame...

Have a look at a full retrofit of the original amp with aftermarket speakers https://www.jaguarforums.com/forum/x...ade-faq-64614/

 

In addition I believe that $55 for a speaker no matter what the name brand is extremely high for a salvage yard. I would expect that $15 tops should be what you would pay for each. Go to www.pullapart.com which is a nationwide salvage yard company and you can find the closet location to you and see what they charge. That should give you a good idea of what you should expect to pay. Good luck with your upgrade.