Echinacea will normally take 10-20 days to germinate at 65-70F (18-21C) - cooler or warmer may take longer. I think your climate is approximately a Z8 and the plants may do better outside than inside over winter with low or inadequate light. You don't need to cut them back, let mother nature take care of the dormancy, give them some protection during a harsh winter storm if your pots would be in danger of freezing. I've moved very young plants in and out of my unheated garage when temperatures have been predicted to fall much below freezing.

The seeds will be hard to miss. The entire stalk will be covered with small round balls which will turn to a tan then dark brown/purple to blackish color. Leave the seeds to mature (late in the season). You'll know they're ready when you rub your hand over the stalk and the seeds come away fairly easy. Watch that the birds don't eat them all up before you harvest.

A good rule of thumb to remember when looking at flower stuff and there is more than one type of thing that could be seed, is to test with your fingers. The seeds will hold together while the other stuff will crumble or if moist roll up in a ball. Viable seeds are always hard and will not easily crush/break under pressure. Remy

I second Cathy's winter sowing suggestion. I've started many native wildflowers this way, using milk jugs. Echinacea purpurea doesn't require a cold stratification period, so you've got some time to put this together. You could try the Winter Sowing forum, or Trudi Davidoff's site for tips. Wintersowing is like having tiny cold frames, so the seedlings can get an earlier start with more even temperatures. You do have to keep an eye on them once temps start to rise, taking the tops off on warm days, and making sure the soil doesn't dry out. After the seedlings have hardened off, you can transplant them into the large (and hopefully deep) pots where they'll spend the summer. I also think cooper8828's advice would work although it's more risky if the weather is really roller-coasty in the spring. Also -- you might try posting this to the Perennials forum. It's a busy forum and plenty of Echinacea experience there.