Cardiff will allow long-serving Kevin McNaughton to leave this summer along with Danny Gabbidon and Nicky Maynard.
Highly-rated Atletico Madrid midfielder Saul Niguez has signed a new five-year contract.
Stoke boss Mark Hughes has made his second signing since arriving at the club, bringing in young defender Marc Muniesa from Primera Division champions Barcelona.
Muniesa arrives at the Britannia Stadium on a four-year deal and with significant pedigree after he helped Spain to last month's European Under-21 Championship title.
His arrival follows the signature of PSV Eindhoven's highly-rated defender Erik Pieters as Hughes begins to stamp his mark on his new club.
Hughes' links with Barcelona, where he spent a season as player in the late 1980s, helped alert Stoke to the possibility of signing a player who, despite trading Catalonia for the Potteries, stated his eagerness to make the switch.
"I'm very excited about moving to England to play for Stoke City and will do everything I can to help the club," he told Stoke's official website.
"It wasn't a big decision for me to make. I came to England yesterday to meet the people at the club and look around the training ground, which is very impressive.
"My season only finished a fortnight ago when the European Championships ended, but I can't wait to get started for Stoke. I would start tomorrow if the club asked me to."
Muniesa made his La Liga debut with Barca as a 17-year-old and was an unused substitute for the Champions League final success over Manchester United in 2009.
The 21-year-old, who can operate at left-back or in the heart of defence, was more recently a fixture in the Barcelona B team, although Stoke still had to fend off interest for Muniesa in Spain before completing the deal.
"Marc has been well-schooled by Barca. Technically, he's a very good player and I've no doubts he will be an excellent addition to our squad," Hughes said.
"I know he's very highly-regarded in Spain and was attracting interest from clubs in La Liga, but he's an ambitious young man and wants to test himself in English football."
Stoke chief executive Tony Scholes revealed Hughes' link with Barca had helped seal the deal.
"Marc has an excellent pedigree, as you would expect from someone who has come through the ranks at a club like Barcelona, and we're delighted to have secured his signature," he said.
"We were alerted to his availability and moved quickly to make him a Stoke City player.
"The whole process was greatly helped by Mark Hughes' links with Barcelona and it's clear to see he's very excited by the challenge of making an impact in the Premier League with us."