I like to plant a lot of spring bulbs in my shade garden. You can plant other perennials (like hosta, astilbe, bleeding heart) near the bulbs to hide the foliage as it dies. Also there are many woodland wildflowers that look lovely in early spring--bloodroot, trillium, spring beauty, Dutchman's britches-- that would look good under your bushes. There are a variety of Huechera that have different colored foliage from deep purple to chartreuse. For the back of the border you can use ligularia, and cimicifuga. Some campanulas also bloom in shade. With a little planning you can have color most of the season without using too many annuals.

From my own experience, I would not recommend astilbe as they really like moist soil and if it gets hot, they just wilt away even in shade. Here is what I have in my shade gardens. These gardens get total shade, or semi-shade:

Epideums
all sorts of hostas
tiger lilies
lady's mantle
primroses
silene
candytuft
salvia
evening primrose
yellow loosestrife
mosses
ferns
bleeding heart
false bleeding heart
woodland violas
columbine
some gentians
campanulas
lemon verbenas

So, a few more to add to your list.

I've recently fallen in love with corydalis. About 1 foot tall tiny yellow long blooming flowers.

Lobelias if you have wet soil, are blooming here now and they are beautiful but you must have wet soil.

:) another fan of the corydalis... it's one of the prettiest foliage plants I've ever seen, and it reseeds freely, will grow in a crack in the wall...and while I don't think much of the flower spikes, they're easy to remove. I've got them growing in almost full sun, and almost full shade (their color is better in the shade) and all from one sad, lonely plant I picked up for a buck three years ago :)

I have daylilies in my shade garden and it appears you get more light than I get. There is shade and there is shade. I also have oriental, asiatic lilies in the shade garden.

Those inexpensive little primroses from the grocery store hold up pretty well and are perennial if they get enough water. They bloom all spring if deadheaded.

There are other fancier primroses too, but I have no personal experience with them yet (since they're not $1.00 at Home Depot) lol

Hardy geraniums come in lots of nice shades of pink, white, and purple, and spread and are very easy to grow with little to no care. They bloom through the summer, after the primroses have said bye-bye.

Hmmm, Charlotte, down here in zone 7 my candytuft didn't do well in shade at all. I moved it to a west facing garage wall under a rose bush and it has grown vigorously. Go figure.

Solomon's seal and Siberian irises will both add some height. If the soil stays damp enough astilbe should do fine - be careful though - the areas close to my house are usually the dryest in my yard. Heucheras would do well. Lenten roses like those conditions. Almost any fern you can think of. Maybe geraniums - don't know how strong the light is in zone 6 - you might need more. Also the annual tourenia for soft color all summer. If I had to pick just one from this list - try Solomon's seal - beautiful from March through frost.

I love the way Lamium fills in and around things, and there are many different ones. Also I planted some Japanese Tassel ferns in my shade and they really look lovely in only a few months.

I like the variegated Solomon's Seal. Once astilbes are established, they really don't take that much care. However, in our Oklahoma heat, the foliage dies back in August, but resprouts the first of September, so you're not without it too long. Eupatorium 'Chocolate' would look great.

I just bought a new shade plant (well, besides the Thalictrum flavum 'Illuminator', which is a GREAT plant) called indigofera kirlesii, leaves opposite, with pink wisteria-like blooms. Even as a new plant this summer, it has bloomed continuously. Gets about 2' tall by 2-3' wide. Striking plant.

Other successes in my semi-shady, dry shady back yard, are campanulas, heucheras, heucherellas, hydrangeas (a dwarf would look cute, like the red foliaged one), Virginia sweetspire, holly ferns, Japanese Painted Ferns, hardy begonia (not the bedding type), Japanese butter bur (petasites variegata), lamium (ground cover), azaleas, hellebores, epimediums (great for dry shade after established), typhonium divaricata (great little ground cover; voodoo lily).

Susan