Yeah, very limiting budget. Finish the room, then start saving as much as you can. A dedicated HT of that size deserves the best you can get. An Orb system is something you'd be looking to upgrade the second you experienced an even slightly better system.
Now with a room that size and starting a build, why would you not consider future planning for a full Atmos/DTS:X or at least a 7.1 system? If it were me (and it well could be in a couple years), I'd be at the stud level with CL2 rated speaker wire in my hand stapling it up for up to at least a 9.2.4 system. Wire is cheap compared to trying to run it after walls are up.
Good luck.