More info is needed to make an informed recomendation. Rod size and line weight, bait or artificals should all be factored into your selection.
You can't go wrong with a Penn Reel, but the 6500 might be a bit large for a rod that is light enough and short enough to cast from a kayak.
Basicly, you need to start with the rod. What test line do you want to use? How many yards of line do you need on the spool?
Select a reel that is rated for that line weight and capacity.
Everyone likes to have a safety margin in both areas, but the superior drag characteristics of a really good reel, make "overkill" less important.
The Penn 5500 SS might be all you want or need and the Penn 5600L "live liner" is a sweet little reel.
There are several other brands of reels that are very good. They all fish well and you will never wear them out. But you will eventually do something dumb, and break your reel.
When that happens, you'll be glad you bought a Penn.