Even going the most economical route, your probably looking at around 500 dollars for a sump, return pump, skimmer and necessary plumbing.
I went with Eshopps when I built the filtration system on my 180, and I'm pretty happy with it. As far as the sump itself is concerned, it's basically just a plastic box that catches water, doesn't need to be anything expensive.
The skimmer is where you might want to spend a little more. I ran a Corallife 125 super skimmer, on a 135 tall for years,( lower middle of price point) and it did great, for the money. It's a little small for my180, and I need to upgrade, but it still does well, I only have 5 fish.
IME a sump is the way to go, no unsightly equipment hanging all around your tank, quieter because it is all underneath, and gives you more overall water volume which helps the stability of the tank.
Good luck ghost!