This thread need Triple8Sol to chime in, he has both and is in the perfect position to give the right answer.
Truth be told, I just got the TT30 and haven't ridden them yet. I did ride the Feedbacks plenty, which are very very similar to this year's SF45, but a couple small differences. That said, by feel, the 2 bindings have a similar highback flex. The SF45's are a little taller, about 1cm, so not as high as your Cartel skybacks (then again nothing else out there is). The main difference is that the SF45 base is a bit stiffer than the TT30, but I can't comment on that difference yet. I think the SF45 will be a much better replacement for your Cartels. That or the DS45.
16 NS West . 15 NS Snowtrooper BIA . 13 Salomon Pow Snake
15 Now Drive . 14 Burton Genesis
14 Flow Hylite