You can do a lot with a basic 500 Jigmaster. Newell, Tiburon, Accurate and other companies have had quite a few accessories for it.
This is one of mine that started out as a run of the mill 500SL. I added a Penn power handle with Newell bars and base along with upgraded drag washers. It's now my heavy boat reel. In this picture you can see the Newell Bearings, they've since been swapped back out for the Penn steel bearings.
This one started out as a basic black 500 which I modified into a 501 narrow spool.
First it got magged for casting then I swapped out the chrome spool and the wide bars for the Penn aluminum spool and the Penn Narrow bars. I also added the Newell base, Newell Teflon Bearings (not in this picture) and a Pro Gear power handle. Like the other reel this one got a new set of carbon washers. This one serves as my backup bridge bait reel (with the Penn steel bushings) and beach casting reel (with the Penn Bushings swapped out for the Newell Bushings) for throwing ridiculously big weight n baits.
There's not much point in adding the Newell Teflon bearings, which are not actually bearings, they're bushings, to the 500. Due to the size and weight of the fully loaded spool it's never going to be a great casting reel.
The 501 is a different story. With the aluminum spool and the Newell Teflon bearings the 501 is a surprisingly good casting reel.
The biggest negative about the Newell bearings is the strength. Being made of molded plastic and Teflon they are not even close to as strong as the stock steel bushings (Obviously). They do NOT handle the intense pressure of winching 10# fish 40' in the air very well. I trashed a set in one night doing that.
If you're going to be predominately fishing up and down, minimal casting, there's no point in the added expense. If you're going to be beach casting with the 501 then you should pick a set up.