Are there other Grado's in my price range ($400-$500) that are worth putting some research into? Or should I just keep my eyes on the HE400 and HD650. And as for the HE500, if I could find one for $600, I would take it, but I have only found them for $700, which is my budget for my total setup, including amp (and possibly DAC), so I am not sure if that is a feasible option.
Grado HF-1 (SR225 drivers with wooden body) come very close to RS-1 and can be picked up for a song. I haven't heard the HE400 so can't help you decide between them and HD650, perhaps someone else can chime in.
Is the HF-1 still available to buy new? I thought that they were a less than 500 unit limited edition run. Not sure what a used one goes for, but I'm guessing that it's a very expensive song for what was originally a $200 can.