Would pre-sliced, pre-packaged fish be considered sushi grade if I freeze it for at least a week before consumption?
I have done several sushi dinners at home: a lot of fun and also a giant saving! One thing that you need to consider is the amount of fish, sushi recipes call for small amounts and so, even if you are preparing straight sashimi, I found that as 'little' as two pound of fish will 'force feed' a team of 6-8 hungry adults. Wish sushi grade fish you obviously don't want to do it wrong and get sick, so I suggest you stay away from home sanitized cuts. The problem is not only the extended frozen period, but also the way the fish has been handled from the moment it's caught. After searching and talking to the best restaurants in San Diego, I found that http://www.catalinaop.com is one of the best suppliers available. I was lucky enough to be able to swing by their warehouse and avoid the shipping cost, but they offer next day delivery at a reasonable price. The quality and variety is outstanding and they are specialists that will answer every single question! Make it special! :) 

Hope it helps :)