I am going to paste a post I made from another topic. Looks like I misremembered the speakers in LZ. I used JL Audio C2-525X (actually around $300 now):
IMO, the correct option for improving the sound is to start with the Pinsound spike 2 subwoofer and line out connector. Anything else you do grabs the sound at the speaker level which is processed after the cheap amp in the backbox. https://www.pinsound.org/shop/en/64-subwoofer-line-out-stern-spike.html
Next up, I like to get the Speaker lights combo kit. You don't have to get the lights, you can do only the speaker plates. I don't like using a 4" speaker. Upgrading to a 5-1/4" is going to get you a better speaker. If you go with the lights (rather than only using the 5-1/4 plates, don't forget to get a matching speaker color surround (On that same page) https://www.speakerlightkits.com/5.25-SPIKE-2-Speaker-Plates.html
Buy backbox speakers. Some people use the Kenwood KFC-1366s that Stern uses on the LE. I wouldn't use those unless you are only driving them from the Stern amp. Those speakers are lower end and the only reason to use them is because they are very efficient so you don't need a lot of power.
What I do for speakers may sound a little silly. I like to get speakers that are at least a mid-end but will match my machine. So for TMNT , Munsters and JP I used JL Audio C1-525x. They have a yellow woofer and are good speakers. For LZ, I went with JL Audio C2-525x (higher end, as these are ~$300). I used Polk for Mando Prem that have a copper colored cone etc...
For the amp, I really like the price/performance of this amp:
https://www.amazon.com/gp/product/B08CJZGT6H/ref=ppx_yo_dt_b_search_asin_title
It uses the TI TPA3255 chip which is favorably regarded. It is class D so it runs small, light and cool. I have the volume knob set to the middle and adjust the sub to match the output level.
You'll also need cables. Get 2 pairs of something like this:
https://www.amazon.com/gp/product/B07D8M5DML/ref=ppx_yo_dt_b_asin_title_o03_s01
Don't forget speaker cables. Whatever you want will work here. I like to use at least 14 gauge (lower number is thicker/better in speaker cables) wire.
I'd get 2 pairs of banana plugs. On that amp I posted above, I've noticed that my normal plugs are a little loose. I've found these fit nicely:
https://www.amazon.com/gp/product/B0895L81BV/ref=ppx_yo_dt_b_asin_title_o02_s00