[j-nsp] MX960 with 3 RE's?

[Colton Conor]

Is it possible to have 3 RE's in a MX960? For example:
http://www.ebay.com/itm/Juniper-MX960PREMIUM-DC-ECM-4x-PWR-MX960-DC-3x-SCB-MX960-3x-RE-S-2000-4096-/271739188162?hash=item3f44eaf3c2:g:Z~IAAOSwnDZT8lpv
shows 3s RE's installed?

The documentation I have seen shows that a MX960 can have 3 SCB's, but it
mentions only 2 REs?

How does the RE-S-2000-4096 compare to a RES-1800X4-16G? How does a the
regular SCB compared to the Enhanced SCB?