Looking at your Zone you might be to cold. There are not any hardy perennial kind like the beding types that I am aware of. Most of the species I am familar with are Zone 6 hardy. But you could give them a try like omeiana, arguta, stenantha, longiloba. If you want showy and willing to collect seeds try balfourii. Another showy annual is glandulifera this should be hardy for you and gets very big like 6 to 8 feet tall if well watered and will seed everywhere but is easily pulled out where not wanted.

Portulaca, helichrysm (strawflower) and nasturtiums make for fine alternatives.

Salvia, verbena, annual phlox, marigolds also might be looked at.

I don't find impatiens all that expensive if planted in a large area.If you plant each plant about 18 inches apart,very few will fill a large area.If they are planted this distance apart,they will fill in but stay low to the ground.If impatiens are planted close together,they will grow tall and leggy,and in my opinion will not look as nice.I have a friend who actually measures 18 ins between each little plant and has the most glorious bed of impatiens all summer.

Hardy geraniums might be a good option. Some are pretty compact and uniform.......and some bloom all season....months and months.