Make sure you really check for smoke, especially on start up. My GTA is burning a lot of oil (not a lot different to yours) and it took a while for me to notice the smoke. There is quite a lot on start up which I failed to spot for a while because I wasn't specifically looking for it, it is easy to miss. Get someone to watch when you first start up the car to see what really happens, and look closely for a small but noticeable amount once it is running.
My engine needs a rebuild btw. I hope there's nothing bad going on with yours but that is a lot of oil, even for a TS. You should get it looked at asap IMO. If you tae it to AutoLusso, they will check it over for you and get it up on the ramp so you ca see if there is a leak underneath.