Question: I suspect being economically strong and independent aren't enough to become a super power in today world, I realised that US is slowly losing it's grip as a super power after it starts shifting focus on other research areas and staying away from making nukes. Given today technology, can a nation become a super power without having any nuclear programme? Sorry for my childish thinking but I think people would definitely listen when you can talk at over 250dB.

Answer: 
China does have nuclear weapons, but I have never heard people citing it when arguing that China is now superpower.

They usually cite their GDP (PPP) or exports in $bn.

If that is not sufficient, consider an non-nuclear but economically powerful country with a close ally (maybe a client state of sorts) in the same military block which has some nuclear capacity but does not qualify as superpower otherwise.
Japan might be considered a super power and they don't have nukes - by choice. Should they change their stance on nukes, they could probably develop them within one or two years.

Their power is mostly through economics, technology and military Allies which are more important in todays world.

Nowadays - at least in the western world - actions are taken through trade deals and trade sanctions rather than military actions. There will be interventions if a country starts an unjustified war.

We saw this in the form of trade sanctions for Russia when they annexed Crimea. (I would like to point out that I'm not saying this was or was not justified, I am merely stating what happened - just in case I want to visit Russia in the future)

We can see how these sanctions or embargos can devastate a country in the case of Cuba or North Korea. Although they might be less effective against large countries.