Simple question, I've done a lot of research and it seems that the standard will do just fine. But are the extra effects you get with the Ultra really worth shelling out an extra 500 bones?
This is ultra only:
http://www.youtube.com/watch?v=68y1gjEHiBM
Here's a thread that might help you choose.
http://forum.fractalaudio.com/threads/31629-I-just-can-t-understand...-Standr-and-Ultra-help
There's tons of threads about this on their site.