I spent four days off of the internet to download the entire series by Torrent. I then spent the next week watching all of the episodes, and I spent the week after that rewatching more of the episodes.
I doubt you'll be able to find the English dub, especially since in the US, they did not show all of the episodes. The first season was cut down to something close to 20 episodes. A few years later, they showed the full second season, heavily edited (they also split the final battle into two episodes, and added a filler episode, slicing apart montage and unused fottage from the last episode). I should know. I taped most of the episodes.
Daidouji ftw, and don't any of you forget it.
However, as for Eriol
(SPOILER) he was doing it in order to ensure that Sakura would be come the master of the Cards. In the dub, more urgency was placed on transforming the cards, because if not, the Cards would rampage out of control like the beginning of the show, only all of them at once, as opposed to one at a time.
In the original, the cards would simply turn into regular cards, which is accurate in the manga, because Sakura does need to be the strongest Magic-user as appointed by Clow Reed. Just why he wanted it is a fairly prevalent question in the Tsubasa and xxxHolic crossovers. In the manga, Eriol is portrayed as more conniving and self-interested. What is also a point is Fujitaka also being a reincarnation of Clow Reed, explaining Sakura's magic powers.
The Sakura Arc starts episode 47.
EDIT: Ahh, beaten to it.