Yeah, I really like GTs. I had to give mine away because it terrorized all the fish in the tank. When I have enough room for a 100+g I will get another one.
One of my Oscars lives in a 65g with a Firemouth. They get along ok. The Firemouth tries to be brave and flare his gills alot, but the Oscar puts him in check pretty quick. For the most part they do fine, now and then the Firemouth has some bumps and bruises.
silver dollers will be lunch unless you can find some larger ones. Convicts are bullies... id try for another oscar just watch out some oscars are very aggressive towards others...
I have been keeping GTs with Oscars for many years. Great combo, I've never keeped them together in anything smaller then a 125 at full size but since this is a growout then id say go GT.. They have awesome color