Graceland isn't open late and it's smaller than you'd imagine.
I splurged and purchased the "platinum" tickets for Graceland. It was a good decision. In addition to the house, we also visited most of the exhibits. I think I would have been disappointed with the house-only pass. The platinum tickets gave us access to other exhibits where we saw boat loads of costumes, artifacts and videos. It's also important to note that Graceland is only open 9:00-5:00 pm Monday-Saturday and 9:00-4:00 on Sunday. And the lines can be long.