Cellphone is indeed a speedsub, and quite decent at that. I usually download Cellphone first to watch, but keep HaroTori for keeps. SEED fansubs is not far behind HaroTori IMO, but I still think HaroTori is the best of the three.

And by "wanna start download it," do you mean the whole series? Because if you do, download Aone's version before the license. Here's a place where you can download almost all the current eps: Seed Genesis. Their batch 1-36 should be in the newest news post.