I actually don't have a garden myself, I'm in an upstairs apartment with just a few pots at the door. So I really enjoy my visits to open gardens where you can see planting on a really large scale. The main borders at Harlow Carr and nearby Newby Hall have some truly stunning plant combinations.
Heleniums are late summer perennials here in the UK so they often go well with Persicaria, Kniphofia (my favourites), Monarda, Agastache, the smaller flowered Digitalis, Eryngiums, Crocosmia, Sedum, Echinacea, Salvias and ornamental grasses.
I lived in Maine which meant I couldn't grow a lot of things like this but in zone 6 you should be able to do OK.
I think if you can plant them in larger groups, say three or five plants together you achieve a much more impressive display.
Best wishes
Sue