I'm a huge tropical fish buff mate. This topic is all about how much you are willing to spend ;)
Tropical is the way to go mate. They're easy to keep in terms of both survivability and maintainance. Cold water fish are very limited and Marine aquariums take a LOT of time to set up and maintain.
If you want a really stand out Beauty tank. I'd recomened you go for the Cichlids in a 120 Litre tank (good living room size). Ciclids are quite aggressive with each other if you mix species, so i would suggest looking at picking up a few German Blue Rams. They are stunning, not overly huge, and relatively placid compared to other cichlids.
A 120L tank with a 150 watt heater and a 750LPH filter will be great. In there i'd put a male and female Blue Ram Ciclid. 12 Cardinal Tetra, and a few little corydoras catfish. A few nice plants in there for the fish to feel secure and you will have a stunning setup for less than £180