Which iPad apps to Purchase?

I am nearing the time to make a decision on what iPad apps to purchase for the class.

1. Forscore: seems to be the most popular music reader in blog posts. However, there are several contenders. But....$4.99 each!!

2. GoodReader: I am not convinced I need this. I have been trying Smartnote, which is free. I don't know if we have enough need for a reader that we can mark up text with. Other disciplines might.

3. Percussive: $1.99 each. I need good electronic players. This one works real good and has good sound. But I'd like something that had more instruments in one package.

For each app I have to decide if I want it for all 15 iPads. Obviously this gets expensive real fast.

Any ideas to help me?