by Simon Crawford
The slick American southpaw ripped away Brook's IBF world title on Saturday night, the Briton forced to pull out in the 11th round with a broken eye socket.
It was Spence's first world-title fight but he is already mapping out a plan to unify a red-hot division.
"Kell and myself are the most skilled fighters at 147lbs, also the biggest and strongest so yes, I do think beating him makes me No 1," Spence, 27, told sportinglife.com.
"I think we gave the fans what they wanted to see and I take my hat off to him.
"Kell is strong, fast and crafty - he lived up to all my expectations. He can also punch and I had to show true grit to see it out.
"I told you I was coming over here to take the title back to America and I did that.
"It's only up from here now - I want to fight [WBA/WBC champion] Keith Thurman and [WBO champion] Manny Pacquiao - my ultimate goal is to unify the titles and become the No 1 in the division."
Spence was fighting outside North America for the first time, but insists he had no qualms about the fight being in Brook's home city of Sheffield.
Although the early rounds were close, the challenger came on strong as he dropped Brook in the 10th before the fight dramatically ended in the 11th.
"I thought I was wearing him down in the eighth or ninth - he was slowing and I tried to step it up," said Spence
"I was hitting him with some good shots and he was standing still a little bit more. Then I saw him blink a lot with the eye that was hurt and I decided to really jump on him. It started swelling up a lot more and the end came.
"I have total respect for him - he is a true champion. I took the belt away from the champion - I didn't just want to fight someone who was ranked for a vacant belt. He gave me the opportunity and I thank him for that.
"He hit me with some good shots but nothing that hurt. I proved a point that I can take a punch from a big, strong welterweight as some people had doubted that.
"The whole night was an amazing experience. I knew the crowd had come to cheer their man on, but British fans are great. I tried to use their energy and even their boos as a positive.
"They did cheer at the end and it was great they showed respect even though their man had lost.
"It was a great experience in my young career, fighting away from home against a champion, the training camp and having to come to the UK a week before the fight.
"It was a legacy-defining fight for me."
