I thought about annuals but I plant so many in other areas just the thought of planting more makes my back hurt!

I think dianthus is a good idea if you want a perennial. looks good all year.

Are they a reliable perrenial

At my last house I had tons of Zagreb. I’m in 5b. They did great - covered with bloom in June, I sheared them in July, and they were at least 50% covered with blooms again in August. They were a good 24” tall, maybe taller.

I didn’t plant anything in front of mine, but there are lots of perennials that would be shorter than that. A deep pink flower wouldn’t be my choice, but hey, whatever works for you.

As long as you give Dianthus good drainage, it's very reliable. My personal favorite is Rose de Mai which is an heirloom variety.

In humid areas, Bath's Pink might be the best Dianthus.

Bath's Pink is quite hardy. I grew it for many years. It will also happily spread.

Maybe sedum Firecracker? It blooms at the end of the season but its foliage is burgundy. Here’s some I propagated from cuttings this Spring:

Hope this helps!