Do you have any specific pallette in mind for the flowering plants?
I would consider adding a trellis against the brick wall with a nice clematis and a climbing rose. If there isnt room for the rose near the wall you could use a regular rose bush.
I have 2 that bloom all summer from June until the first frost. On the other hand, roses require a lot of care and can be disease and pest prone. Having brown tattered leaves near the front door can be discouraging.
Another idea is a peony. They love lots of sun and even though they dont bloom for long, they are quite a show and have beautiful foliage.
Along the front of my sunny bed I have sedum autumn joy which I plan to start pinching for lower, more compact plant and a very nice yellow low growing Sedum, kamtschaticum.
If you are looking for some annuals to fill in the space for the interim I suggest salvia. Last year mine really helped a bed-in-transition look quite lush. I dont remember the variety but they also bloomed most of the summer. I heard they might even re-seed but I am a compulsive weeder and have a tendency to pull out the good with the bad. No matter though because I have some perennial salvia seedlings going strong.
Good luck, I cant wait to hear other suggestions and what you finally choose!

oh wait, I forgot to mention one of my favorites, threadleaf coreopsis. It has nice airy folliage and abundant but subtle blooms and I think it looks wonderful combined with any plant. It is just the right height to go almost anywhere and mine looked nice with the folliage left through the winter (along with the sedum).

If you are like most of us, you will spend years fine tuning your bed moving, removing, adding, to get it just right.

The things I always consider are:
1. Plants that bloom over an extended period so I would use my space to the best effect.
2. Plants that bloom on a staggered schedule so there would always be color.
3. As gfult suggested using a trellis to get extra height and added space.
4. Pleasing color and foliage combinations

In the first category: roses like Knockout or Carefree Sunshine which have attractive foliage that is disease resistant and they do bloom from late May to hard freeze. Perrenials: Rudbeckia Goldstrum, hemerocallis Stella de Oro, salvia May Night, echinacea , coreopsis Moon Beam, corydalis lutea, gaillardia, nepeta, perovskia, sedum Autumn Joy. All the above bloom over a long period and have no disease or insect problems in my garden. Also, they would all look good with a background of boxwoods.

The only problem with the above plants is that they donÂt bloom early (except the nepeta which blooms early and late) so your bed would be without color in the spring. You could mix in some early bloomers like: tulips and daffodils and then iris, peonies, and alliums.

I have a very simple planting in the front of my house (unlike the back which can be a bit overwhelming LOL). I keep it simple so that I can keep it neat for the neighbors.

The bed has 5 Walker's Low catmints, a large mass of Sedum Autumn Joy, the spreading Clara Curtis mum (soft pink) acts as a sort of groundcover early in the season, and more than a dozen small-sized daylilies on the outside edge(all different varieties in pale creams or very light yellows (with dark eyes) or solid color ones in deep wine/burgandy/deep rose. All the daylilies are 18 inches or less in size & have 2-4 inch blooms. A long time ago the bed had all Stella d'Oro dls, which worked very nicely, but I got tired of the color and changed it. The bed is centered by a weeping cherry tree.

I have the boxwoods, as you do, wrapping the edge (in my case this is the inside edge, away from the street, but edging the approach sidewalk to the front door) for a sort of formal look.

Since my house faces north instead of south as yours does, I have mass-planted albo-marginata hostas in the front next to the house and evergreens. Across from this is the perennial bed that I am talking about. You can see a picture of part of the bed in the current string "Floppy Catmint". As I mentioned in that string, I do prune these hard if they even think about flopping, because my neighbors are not necessarily perennial lovers. I get nice early bloom, prune into a formal look, get more blooms late in the season.

The bloomtimes of the dls are staggered, rather than blooming all at once as Stellas and others do (that was a decision I made deliberately when I changed colors). Stellas would work for you if you like the bright golden yellow with your red brick. Nothing really blooms like Stella, but Happy Returns is a softer yellow which is also very long blooming. There are also lots of small red dls that are fairly long blooming that would work for you, Little Business, Pardon Me, & Little Wine Cup come to mind. A nice smallish pink dl (not mini) with red eye and a neat look is Strawberry Candy.
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that I also have this bed underplanted with crocus. I used Crocus vernus 'Queen of the Blues' which I bought in quantity from Van Engelen. John Scheepers, their sister company, is a good source for smaller quantities of bulbs.