Diamond on SERO Question

[2 Bunny]

The other day, I thought I could perhaps get a better deal on cell service and thought I might buy one of those ultra rare $30 Sprint SERO plans on eBay. I had heard in threads around the community that Sprint jacks up that price to $50 for some smartphone users. From what I understand, the Touch Pro 2 is the newest device that is allowed at the $30 rate. Would I be correct in thinking that the older diamond should also be equally compatible with this plan? I would like to just verify this for sure to make sure so that I know I can activate the Diamond on one of those plans without finding out that it can't be done that cheaply after spending $100+ on eBay.

Thanks in advance.

- 2 Bunny