>"Can anyone tell the best pre-emergent?"

Actually, no.

See pre-emergents are like car insurance - a preventative, an insurance. A policy for me may not be best for you and visa-versa. It really depends on what exactly you are trying to 'prevent'.

There is pendimethalin, such as Scotts "Halts" and Lesco's "preM" which is a true pre emergent for grassy weeds like crab grass.

There is dithiopyr, used in "Dimension' which offers pre emergence and a little post emeregent protection for grassy weeds and some broad leaf weeds.

And there is isoxaben, used in Gallery / Portrait which offers pre- emergence protection of broad leaf weeds only - nothing for grassy weeds.

The brand name on the bag means nothing. No one brand is better than the other brand. What is important is the chemical/herbicide inside. Check the label for the active ingredient before you buy and buy what suits your need.

You used STEP1, which is a combination product, a one size fits all for weed prevention and fertilization and found out that you were too late to prevent weeds ..... and too early to fertilize the grass!

Another way to think about these combo products is to compare them to cold medications. Brand X is the do it all, fix every cold symptom. But why take the decongestant part if you have a runny nose and only need the antihistamine part?

Don't fall for the marketing hype of a do it all fix everything product - it's just advertisement!

You mention crab grass. Halts (pendimethalin) will prevent crab grass. Your local Ace Hardware sells Halts, without any fertilizer.
Ask you local store to order it for you - support your local business in these times. Tell the stock number which you can find here http://www.acehardwareoutlet.com/%281o45vx45zc1gmv45aldj0i45%29/ProductDetails.aspx?SKU=75086
If you must, Ace Hardware Corporation would be happy to ship the product to your door step via an on-line order.

Apply the Halts in early spring first. Throw out the calendar, just use you eyes and watch nature. When you see the tulips popping, the daffodils and crocuses growing. The forsythia bushes turning yellow - IT'S TIME.

Then, after you start cutting the grass because the warming sun and spring rain is making it grow, it's time to fertilize - feed it.

Follow up with a general crab grass and broad leaf weed killer, spot spraying any weeds that do germinate during the spring and summer ... and you're basically done until Labor Day, having a crab grass free and thriving lawn.

Try Snapshot. I tried it last year and it worked excellent.
And yes it stopped crabgrass.
I did not have any yes any new growing weeds on my lawn.
I used it again this year. One bay lasted me 2 years.

I use surflan AS for a pre-emergent on my empire zoysia. This was the first year I gave it a try. Last year my lawn was covered with goosegrass, dallisgrass and some crabgrass. This year I have next to none of any of the above. I controled the dallisgrass with fluazifop mixed with triclopyr. I have a good recipee, it controls all types of grasses in the zoysia and doesnt harm the zoysia at all.