Larger tanks are more stable. End of discussion.This can not be argued
If the sky is the limit, I would start off with a 75+, which would give you freedom to go in a lot of different directions with the tank. You could easily keep 2-4 schools of tetras/rasboras, you could keep a handful of smaller cichlids such as electric blue acaras, do a biotype. The sky is the limit. Personally I would even shoot for a 120 or a 125, with the 120 having the advantage of better dimensions (4x2x2). You can typically find 75+ gallon tanks on craigslist for dirt cheap.