I'm assuming you are only looking for the rears?
I think for mostly street and only some auto-x, the stockers are good enough for a while. If you really want to upgrade them, I'd recommend something adjustable (unless you want to swap out fronts as well to match rears and car handling/balance). The only adjustables I've seen that I would consider are the Steeda one or MM one. I don't know anything about the Eibach ones.
Main take away: if you aren't staying stock, get adjustable ones. I wouldn't replace the stock one with another, different non-adjustable bar (unless you are prepared to have several different bars with you at the track and are willing to swap them out). If all that sounds like a huge PITA, then I'd say you are at a stage where the stockers are sufficient for the time being.
FWIW: I've thrown the car around quite a bit at road-race tracks and auto-x, and I have stock fronts and rears. There was some body roll (that I'm addressing with coilovers currently, not bars).