It depends on what type of vented you're talking about.
The discs on Si's are vented as standard. What that means is that the middle of the disc is vented (like two plates stuck together but with vents in the middle of the two), and then you can get vented discs which are what you see with the lines on the actual disc. It's meant to help cooling of the discs. Don't get drilled, there's no point, and they are known to crack.
The standard system on the Si is more than adequate if it's all in top notch. I replaced my discs, pads, calipers, and had the rear drums fully rebuilt with new shoes and cylinders and the stopping power was fantastic for what it was. I'd be confident in using it for a 2ltr transplant as I know how good it is when it's in perfect running condition!
