I went HID in the standard lights and imo it's ok. Much more visible to other road users and the road is a lot more visible at night. The main downside of going hid with high beam as well is that it takes a second or two to reach full power. I'm not too bothered by that as I ride very little at night. It's never been a problem for me as such, but something to be aware of in case it might be for you.
I have something similar to the kit you link to, but not identical. It will likely make a very noticeable difference. The ballasts on that one do look a bit chunky though, which will make them harder to secrete away inside the panels.