One of the important considerations when choosing a link is can your suspension tuner setup your shock for that link. They work differently from one another, and the way I understand certain ones have certain trade-offs which you may or may not be ok with. The links are not just plug-n-play, you'll need to re-spring and likely re-valve your shock.
I use Thermosman, and he recommended the Lee Cycle (Jeremy Toye) link for me and was able to setup my JRI shock for it through the mail. It came with bearings. http://www.leescycle.com/parts/lees-cycle-products/
Dan Kyle also seems to have good reviews and is able to setup Ohlins shocks for his link, so he's another good option.
With either option, you'll probably have to remove your shims.
If you don't have an aftermarket shock yet, I would save up for that before a link.
What the link will help with is exiting the corner. As you open up the thorttle hard, leaving a corner, it will not want to just drive out to the outside of the track right away.
For mid-corner, it's going to be more suspension setup, ride heights and spring-rates, and of course, skill. The links will change your ride height and rate of compression, so it might cure some mid-corner issues if you are too soft (usual Gen 4 issue).