Ciaran Clark and Mohamed Diame have arrived at St James' Park from Aston Villa and Hull City respectively with both additions thrilling Benitez as he continues to prepare his squad for the 2016/17 Championship season which kicks off this weekend.
Irish central defender Clark, 26, has penned a five-year contract with the Magpies having spent his entire career with Aston Villa.
"Ciaran is a very versatile player, as a left-footed centre-back he can also play left-back and also as a defensive midfielder," said Benitez.
"He has a lot of experience of English football and will add good balance and competition to our squad.
"I am sure he will progress with us here at Newcastle, we are very happy for him to join us."
Meanwhile, 29-year-old Senegalese midfielder Diame has left promoted Hull City to sign a three-year deal with the Toon, becoming their eighth signing of the summer.
"Mohamed is a strong, attack-minded player with a lot of fight and determination to his game," added the Spanish manager.
"He is also someone who will provide the team with goals and assists from midfield.
"He has good experience of the Championship and the fight needed to win promotion, which will be important for us."