Grass and Clover Took Over my Bed

What a mess! I built a layered bed a few years ago by digging down about a foot and planting moisture loving plants. I mounded up the dirt and put plants that don't like wet feet at the top, then filled it all in with about a dozen different ground covers. The picture I'm posting was taken 2 years ago when the bed was pretty new. Last year it was really full, and although the clover and grass had started popping up I was able to control it by hand.

This year the weeds completely took over. When I tried cleaning it by hand I found plants buried so deep in clover that I'd forgotten they were even there. In total frustration I dug up the worst spots (saving as much of the ground cover as possible) then hit it with Round-up. In essence I'm pretty much starting over with one entire layer.

I sprayed the Round-up 3 days ago, and yesterday I started breaking up the ground to replant. The ground is very 'tight' which I imagine is all the grass and clover roots. My first question: Am I OK to replant now? Can I be sure I've effectively killed off the intruders? I sprayed those spots 2 days in a row (I don't believe in overkill when it comes to weeds) but how can I be sure it won't come back? I'd really like to get the ground covers replanted before they're stressed even more, but I'm nervous. Once that clover gets a hold it's so tough to get rid of and spreads so dang fast.

And of course my 2nd question is how to take preventative steps so I don't have to go through this again next year or the year after. The ground cover gets so thick that it's almost impossible to spot treat. I've been wondering about products like Preen or Over-The-Top. Would either of those be effective in such a thick bed? Or can you think of anything else that might be?

All suggestions would be MOST welcome,
La

LOL! Thanks anyway, but I've replanted and will cross my fingers and hope for the best.

I've had a bad infestation of white clover and pig weed this year. Husband moved several loader buckets of infected rotted manure and I spread it far and wide. The clover popped up in the lettuce and radish bed and spread into the beets. The more I pulled the clover the more it seemed to spread. Since I still had food quality veggies growing near by I didn't want to spray with Roundup so I gathered up my black plastic and clear plastic and started covering the affected areas.

I put the clear plastic over the lettuce bed right up to the beets which I will pull this weekend and as soon as they are pulled I'm putting the clear plastic over the bed. It's best to till the soil before covering it with plastic but that wasn't an option for me. The hot Missouri sun cooked the clover and I just love to walk by the defunct lettuce bed and see the clover brown and rotten under the plastic.