Kentstar - I know absolutely nothing about flowers and their spacing requirements...but, I know quite a bit about laying things out from different designs. If it were me, I would take the same approach that people who lay tile floors use....You work from the center outward. This way, most of the bed will have perfect 12" squares, and all of the outer perimeter pieces are smaller, but the same size all the way around.

EG

And, of course, begin with the tallest plants in the center, work your way out to the shortest around the outside edge, group like plants together for a mass of color, and don't keep everything exactly symmetrical. I'll bet someone over in cottage gardens could help you, they have some gorgeous flower beds there.

Granny

Here is a link that might be useful: Annie's Kitchen Garden

The problem is...
The bed I built is on a strip of lawn that runs between a wheelchair ramp and our walkway up to the front door. So the bed is up almost against the wheelchair ramp (didn't have a choice in that as we have limited space). So I think it has to be planted starting from the ramp side out.

Then why don't you try grouping them something like this (you'll have to know how tall yours get, of course)
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Photo courtesy of Better Homes and Gardens

Granny

Here is a link that might be useful: Granny's Blog

I worked on this for a while, and here is what I came up with. It looks OK on paper, but I'm not a landscape designer, so I'm not sure how it would look in actuality.

Allium Ambassador 5 50" - dk. purple - 5 per sq. foot
Allium Globemaster 5 32" - violet - 5 per sq. foot
Allium White Giant 5 32" - white - 5 per sq. foot
Echinacea Sunset 1 26" - orange - 18" spread
Early Sunrise Coreopsis 1 24" - gold -12" spread
Echinacea Sunrise 1 24" - yellow - 12" spread
Apricot Impressions Tulip 24 21" - apricot - 4 per sq. ft.
Sunny Border Blue Veronica 1 20" - blue - 12" spread
Corps de Ballet Tulips 125 18" - mixed - 4 per sq. foot
Daffodil Dbl Campernelle 24 12" - yellow - 4 per sq. foot
Daffodil Lemon Glow 24 12" - yellow - 4 per sq. foot
Aztec Gold Veronica 4 6" - gold - 12" spread

Bonfire Euphorbia (I just couldn't seem to work these in to the color scheme, but they are 12" tall with a 16" spread)

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Here is a link that might be useful: Annie's Kitchen Garden

Pretty good anniesgranny! I did the same thing on "Paint" on my computer. I have a Plan A, a plan b, and plan c, and even a plan d! I like your combinations. I wish I knew how to post a pic on here so I could show you what I came up with too.
Gives me some good ideas though. Thanks!
I did come up with one solution for all the Corps de Ballet tulips.
Since they are more like annuals anyway (or at least those particular ones) I have a rose garden I will put about 50 in, and I have a small ornamental tree (Caragana Walker) that I will put another 50 around. That only leaves me having to put 25 or so in the raised bed. I will group them too.
I have worked out a plan that hides any of the foilage from the daffodils and tulips, and also goes like the Better Homes and Gardens pic where the talls are in back, mediums next and small plants near the border.
I guess I will see when I get out there and plant how it goes! lol

kentstar, I always start off with a plan, and color coordinate everything on paper. Then, when it actually comes time to plant, I just do it....no plan, no nothing! Same with my veggie gardens. It's more fun to just get wild and creative as I go, LOL!

Good luck with the flowers, and be sure to take pictures! Someone here will be glad to help you with that.

Granny

Here is a link that might be useful: Granny's Blog

I think when someone buys 125 of anything on one shopping trip, then it's well within the clinical boundaries to proclaim the following....you are officially diagnosed!!!

CHAD (compulsive horticultural acquisition disorder)

The good news is that GW IS the prescribed support group and 12 step program. The bad news is, that the prognosis is not good, you will find yourself wanting more and more PLANTS, and nothing anyone tells you will sway your decision to stop buying more plants :)

We will be here for you

I here this disorder is very common. lol
I have to admit, "I have a problem", there! I admitted it, and that is the first step right? lol I solumnly swear that I will uphold the constitution of gardening, and always buy more plants! I will probably run out of yard before I stop. lol