Yeah, Iron is the key. Don't waste your money on high-dollar Scott's and other brands that are high in nitrogen have lots of filler labeled 'weed control' but don't offer enough of what our Colorado soil needs: iron.
I get Green-N-Grow at our local Co-op off of Mulberry & I25. It's only $20 a bag and lasts me quite a long time. It's higher in iron so you want to sweep your walks, drives and patios after application or you'll get rust spots but other than that I love this stuff. Costs a fraction of what the big name brands do at the big box stores plus I use less because it works better. The closer you are to the mountains the more iron your lawn likely needs. When you get proper feeding you'll use less water too. Careful with this stuff though, if you get it on too heavy you'll have to mow every 2-3 days so I suggest a light application and then a week or two later another light one until you get the dosage right.
If you're lawn is healthy enough weed control will be a none issue because the healthy grass will choke out the weeds naturally. I spot treat dandelions (having neighbors upwind who don't care about their lawn sucks) with Weed-B-Gone and weeds in rock beds either get Round-Up or pulled by hand. I end up spraying probably one dandelion per week at most on average. Get your lawn healthy and you won't have to deal with weeds. Crab grass is the most challenging thing I face along the front sidewalk edge because of neighbors upwind and uphill coupled with the fact that that sidewalk is south-facing so that section of soil dries out quicker than the rest making it difficult to keep as healthy as the rest of my yard.
When it comes to lawns, I don't mess around.