I wouldnt say there is such a thing as overkill unless you went really crazy.
I ran a 250W MH over my last FOWLR... sure, I didnt NEED it, but it made the fish look amazing with the shimmer and my LR actually grew stuff.
Now, I wouldnt run 5 250W MH over a FOWLR, but one is fine imo. Same with running T5s, you dont need to go completely nuts and have 2000 watts of T5 over your 180 but the better lighting you have, the better your fish and your tank is going to look.
I recently switched to LEDs and freaking love them. I'll never go back to T5 or MH.
If you're the handy type, look into building your own LED setup. It's really not that bad, my brother just set his up for a freshwater tank and it is AMAZING how much light he puts out. He only runs his LEDs at 50% because of the brightness, and the sweet thing about LEDs is if you run them at 50%, they just last twice as long. So his 50,000 hour LEDs are now 100,000 hour LEDs. That's 23 years of life...
Anyway, T5s are fine. If you want to spend a little more money up front and save it in the long run, try out LEDs. Also you get the nice shimmer effect which is cool to see in a FOWLR, plus a huge savings on power and bulb replacement.
I paid $300 for a premade LED lighting setup, where I typically would have paid about $150-$200 for the T5 equivalent. However, one time replacing all 4 bulbs in the T5 fixture would put me almost up to the $300 mark I paid for the LED and then next time I replaced the bulbs it would push me well over it, so I figure my LEDs are paying for themselves real soon here. Plus the savings in power is not negligible, that adds up over time. I expect to use this fixture maintenance and bulb replacement free for at least 10 years, that's just crazy talk imo