That's cool,
By the looks of it, secondhand ones go for around $500. Not sure what the differeces are between brands, but maybe stick with a big brand (Cusco, Nismo, ATS etc..) if your unsure.
Another thing is that your rear tyres will wear a little quicker than normal. This is due to the skipping, plus the fact that they are so fun to drift with
The HICAS is totally seperate to the diff, so you will still need the HICAS lock bar if you want to disable it.
J