Poyet's side are currently ninth in the Championship but the Seagulls are hoping to launch a push for the Premier League in 2013.
And the Uruguayan manager has pointed to Jason Roberts' winter arrival at Reading last season as an example of how one signing can transform a team's fortunes.
"Reading was one team before Roberts and a totally different team after Roberts," said Poyet, quoted in the Daily Express.
"If you can bring in that kind of player then you have a great chance. For us at the moment it is not possible, but I am trying to convince the chairman.
"In the five or six games we didn't win at the Amex - if one of those players had been here, I'm sure we would be big contenders for the top two."