The 5DIII pretty much makes 3200 classified as "normal" for ISO range Man, if I can push for that camera then the jump from T1i to that is going to be amazing,800 is already so noisy, and the loss of all the DR at anything higher indoors~
for most normal print jobs the 5diii is useable to ISO 12K or so, 25K in a pinch. If you are printing very large then maybe scale back to 3200-6400 max. For the web, IMHO, you can probably push it a stop beyond 25,600 depending on the use.
Thanks Rusty . Mine was taken with a 50/1.4, it handles low light focus really well even at outer points. I do have a 24-70L (Mk 1) and although good I really like he 50, it's always my preferred lens in that range unless I really need to zoom.