are you looking for a used kit? there aren't a lot (infact its pretty rare) of Mental Addiction or HiBoost kits available used for sale. though you can get some older spool and BEGi kits. they were just around longer and some of these people have upgraded to the newer kits, or sold their cars...
good luck finding what you want. but if you buy one of the newer kits on the market you really can't go wrong, it just comes down to personal taste, and how much you want to spend vs. what parts you want inculded.