When I was there in 2003 I did 2 dives in Arinaga with Blue Ocen Divers but then I wet up north to La Palma to dive with Buceo Canarias. If you like wrecks go there! It's not as touristic as the south so it's probably not as known as other diving centers but it was very good. In 2003 they already had nitrox and were very friendly and professional.
I dived the Kalais, a 110m wreck at 30m depth, the Arona (100m at 35m depth) and La Catedral (The Cathedral), which is composed of a series of caverns and tunels, very wide and beautiful at a maximum depth of 40m.
Their website is in spanish only but here is the link:
Buceo Canarias - Quienes somos
If you go to "Inmersiones" you can check the diving spots I just mentioned and others more.
And in "Contactar" you have their address, map, phone number and you can leave them a message.