You can go to the very bottom of the store and exchange for whatever extra credits you'd spend. 1 EC per speaker EC = orange where it says your money
I think it's when you open like 5 Dorms or more possibly you start to get speakers daily. The max they can give you is about 25 but if you're willing to actually use money to buy some credits you can go buy some more speakers in the store and yeah you can have more then 25 if you want but I think with 25 speakers you should be fine. Unless you're one of those people who ignores Club Chat constantly and just talks on Campus... ( half the people ) anyways bye