His super speed has been useless the whole Hueco Mundo arc. It was super fast when he fought Byakuya but since then everyones been keeping up with him.
Ichigo with bankai and mask
I dont think he could beat Stark. Stark didnt seem too strong because he didnt show off a lot of moves, but he was still the #1 Espada. He man-handled both Rose and Love when they had their masks on and they've both been Captain-class for over 100 years.
Ichigo with bankai and mask got destroyed by Ulquiorra and he was #4. In fact, if I remember correctly Ichigo got killed by Ulquiorra. He barely won against Grimmjow (#6) and he got tossed around by Tesla (Nnoitora's fraccion). The only reason Ichigo won against Ulquiorra was because he transformed into that hollow form.
Ichigo in hollow form
He could probably beat Stark. He can use Cero, Sonido, high speed regeneration, and probably other hollow stuff. It's still hard to know for sure because its hard to compare his strength with Starks.
Ichigo as Getsuga
Mugetsu = Win.