I second (or 14th, I lost track...) the HSC decision. It's a really fun workout, with a lot of work involved. HSTA involves a big dread factor for me with the leg presses. I'm sick of them! But I know they work...
Anyway, HSC is really fun and quite varied. You can probably get away without the topper, although she does use it quite a bit- not just for leg presses but for cardio segments as well. HSC also has an abs segment at the end, unlike HSTA which has no abs.
Have fun!!