A few people have been scammed on the site, Only use paypal to pay for items for sale by other members. If they will not use paypal, its likely a scam NEVER SEND E-TRANSFERS OF ANY KIND.
I installed the regular sound bomb. I don’t think you need a split horn unless you’re doing something special. The lack of relay can also blow a fuse in your system. I am not electrically inclined but I still managed it without too much issue.