And off topic: is it possible to use AirPlay to Mac mini? I heard someone developed a program but that it didn't work too well, but this was a while ago. I can't find it though, forgot what it was called
The answer is no. The API's to access the Java Nitro engine used in Safari are not accessible to 3rd party apps.
As far as "huge" speed differences, I would beg to differ. Sites that are heavy in Javascript perform much better but overall any speed differences are usually small.