^ PP, maybe those are the two frames the OP narrowed them down to. I commend him for that vs. listing 5-7 frames he might be interested in. At this point I'm not sure he really needs to defend why he is interested in those two frames. He just needs some advice to help him narrow it down some more.
chris217, I think both are great frames and you will be happy with either. I assume both frames would be used or have you found NOS (new old stock)? If there is a difference in price between the two, that might help sway your decision. Both should be stiff enough for you. I am close to your weight and have found the 585 to be stiff enough for me. If you are worried about that, you could always go after the 585 Ultra version. The 585 is a very comfortable and stiff bike. I could ride the whole day on that thing. I have no experience with the Time, but I have also heard very positive things about them. I don't think you can go wrong with either.
I don't know the geometry of the Speeder, but is it similar to the 585? I know someone will mention this, but make sure you fit the frame comfortably. Since these very well could be a used bike purchase and you might not be able to ride them, try to find a bike with a similar geometry and make sure you are comfortable with that. Good luck with your search. I will be happy with either one of them.