Heather in containers

As September approaches, I've been thinking about changing the plants in the urns on my balcony.  There are still flowers, but not as many as I'd like and the display doesn't look tall and bushy enough. 

Researching container options for fall/winter, I came across a nursery that specializes in heather.  Wow! I had no idea it was such a colorful winter bloomer and that literally hundreds of varieties are available.  I immediately went into research mode, trying to create a short list of my favorites.

I'm eyeing Erica x darleyensis 'Dunreggan':

Erica x darleyensis 'White Perfection':

Erica carnea 'Golden Starlet' mostly for its foliage color, a bit for its growth habit:

Erica carnea 'Lake Garda':

and Erica carnea 'Clare Wilkinson':

I tried to find plants that would bloom white in winter and grow as tall as possible, while avoiding the true heathers (Calluna vulgaris) because they need acid soil which might upset their container-mates.  (I'm not sure who those container-mates will be at this point, but I'm trying to keep my options open.)  Unfortunately the tallest genus and species is only hardy to Zone 7, which of course is too tender for a container garden in Boston.  I also chose a couple of heaths that bloom pale pink or purple because I have a feeling that in January, February and March (but not before then!), I'm going to want to see a little color peeking out from amid the green and white.

I can't believe I've never considered heathers for the winter garden before and I wonder why aren't they more discussed.  From what I've read, they would really like the growing conditions at our beach house too.