some things to think about...
prioritize on what you think is most important, oxygenated wort makes yeast happier and a stir plate makes more yeast. With the caveate that most sources do not recommend using a stirplate with dry yeast.
Two things that might bias you towards a stirplate, big beers or lagers. I would consider how big your beers are because if they are over 1.060OG some think you should be either double pitching or needing to do a starter. The same goes for most lagers. In that case I would look at a stirplate.
The O2 thing can be fun and might help all kinds of beer. The things to consider with that would be the source for the O2 canned or pumped. After reading from many sources I came to the conclusion that either works but there are tradeoffs. You can get pre-made solutions from most of the vendors on-line and the only real difference in use is the time it takes to oxygenate the wort. Canned O2 can be done in less than five minutes and a pump can take 10 minutes to half an hour.
I got a stirplate first and then built a pump based 02 aerator using parts on sale for less than $25. I was making a lot of big beers and didn't want to spend the money on yeast.
If you go for a stirplate get a second stir bar and really strong magnet to trap the stirbar when you are doing a transfer, if you dump one you still have a second

Also get a 2,000 ml beaker that is substantial enough to move from the stove top to an ice bath.
If you decide to go with an aeration kit make sure that the aeration stone is 2 micron for canned air or 5 micron for pumped. If you pump you need to have a fish pump that is rated for at least a 20 gallon tank and a sanitary filter. Another reason I went with the pump for aeration is I didn't want to babysit it. I put my aeration stone at the end of a stainless tube and drop it into my fermentor so it aerates while I am cleaning up. Set it and forget it works for me.
Hope this helps.
-t