How coincidental, i *finally* got round to resolving this just the other day
Went to the tops, convinced the gangster at the reception that benny was going behind their back earning extra money and trying to kill mr house, so they gave me his room key.
Searched the room for stuff, found evidence of his betrayal and the "yes man".
Told the gangster and he gave me back my weapons to deal with him.
Talked to benny and convinced him we could strike a deal in his penthouse, but ONLY if he went there alone.
Talked to him a bit in there, he offered to work together, i didnt trust him so i whipped out the trusty double barrel and shot him is the head, veronica and rex finished him off before i could reload ^_^
Retrieved platinum chip.
DAMN the speech skill is handy!