TZ,
I looked up the list of potatoes that you received last year and I hope they do well for you this year. You have clay soil? Organic matter to the rescue.
I would definitely add organic matter....compost...peat moss..etc to the row as you drag it out. Mix it in a bit and then transplant those TPS seedlings. Any amount to make the soil friable and not gummy. You may have read what I put into the soil on the spacing thread topic.
Meanwhile, it doesn't hurt to read what you local area says to do with clay soil....
http://local.garden.org/Improving_Cl...Vernon_OH.html
http://local.garden.org/Testing_Soil...Vernon_OH.html