I would say it depends on where you live and how protected the planting site will be. I am out in the country where the wind blows so I don't plant anything before May 15th just to be on the safest side. If I lived in town where the wind would be blocked, I would be more adventerous and maybe set out new perennials around May 1st. If you're going to be planting on the south side of a building or fence and they'll get full sun...I might even put them out now and cover them if a frost is forecast. The one thing about early planting in the spring is that it does do wonders for a plant.

I still have shrubs that I overwintered in my garden, sunk them in the dirt in their pots, and I won't dare to get them out until the first of May when I usually have the garden tilled.

Most hardy perennials won't even be fazed by freezing temperatures - certainly not the ones you mentioned. Go ahead and put them in the ground! They'll thank you for the head start later.