Runescape item question?

Ok so I have a bandos chestplate and like drag legs boots and gauntlets an abyssal whip a tzknot shield and a neitiznot helm. I have about 2.5mil in cash that I'm willing to use. I primarily do slayer with sumona and already have a cannon and thousands of cannonballs. Should I sell my whip and then buy a bgs? Or keep with what I have now? Or sell my bandos top and buy a dragon plate and bgs? Orrrr is a gs not good for slayer and I should stick with my whip? Thanks for answering 10 points