If you have 75G already on hand; it will be OK upgrade from 40G with additional foot in length. Still; not sure if that is enough space for 2 full grown large males and one female. If those guys are huge; a 180G might be a better choice to create a spacious water/dry combo enclosure.

IRT filter, the biggest you can afford is my answer. The API Filstar XP-XL (previously Rena XP4) or a Fluval FX6 come to mind .