Here's what your problem is. You want an instant cycle. The problem with that is bacteria only grow so fast.
If you don't have any other fish in the 30 gallon, I would transfer the filter with the media to the new 55. This will give you good results and you will have little to no cycle, because you are using an established bacteria colony. But, you also need to put the permanant filter on so that some of the bacteria will begin to colonize that filter. Give it about a month, and then take the media from the older filter and squeeze it into the other filter, and remove the smaller filter. At that time, you will have to cycle the 30, but it will still have a head start. This only works if you have no fish left in the 30, and if you wash the filter media in the water you remove during water changes.
If you DO have fish left in the 30, I would transfer as much gravel as you can fit, remember that only the first inch or so is usefull in this situation. Put as much as you can fit in your filter (if you have any room) into some nylon sacks (nylon stockings). Put that in your filter, and the bacteria should colonize the media from there. This has a relativly low population of bacteria, so I would recommend washing (in tank water) your media from the 30 and put it into the filter of the 55 (if they fit, you may even be able to use it as 1/2 of the main media).
The main theory is to get as much bacteria into the 55 as possible. Beneficial bacteria only grow on stationary objects, and in greater number with good flow/high oxygen. The rock, and gravel was a good idea.
Your readings don't mean you're cycled, it means that there's no/very little waste. This means, that as soon as you put waste producing fish into the tank, their waste will turn into ammonia, the bacteria will build up to meet this need (about 1 1/2 - 2 1/2 weeks) and produce nitrItes. Then the bacteria that "eat" nitrItes will build up to meet this need (about 1 1/2 - 2 weeks) and produce nitrAtes. When ammonia and nitrItes reach zero consitantly you are fully cycled. Any change in waste production will result in a "mini-cycle".
Therefore, I would recommend starting will an established colony of bacteria and just use the oscars to complete the cycle. This will result in a shorter cycle period, and less risk of fish loss. I don't recommend the use of chemicals or "Encapsulated bacteria" simply because I don't have any experience with them. Good luck and Good fishing!
Edit: Opps
, I didn't look at page two. Guess, you know most of this now, but I'll leave it up.