Newest Tivo model that will work with DirecTV (SD)?

After a number of upgrades, I have quite a collection of retired Tivos (Series 2DT, Series 3, Premiere) that have all be used with Comcast. I have a second home in the mountains that has DirecTV (SD service - HD is not available due to line-of-site) with a Tivo Series2 single-tuner (standalone, not integrated DirecTivo) that has been faithfully chugging away for close to 10 years with no failure.



My question is, despite this unit running fine, I was wondering if it makes sense to swap out with something from my graveyard? What's the latest Tivo model that can operate standalone with DirecTV?



I am hoping that once DirecTV's new satellite 14 comes online mid this year, I will be able to receive HD programming and will upgrade to a Tivo-compatible HD receiver.



Thanks!