Yes. If you really want a demonstration of what is possible with hardy annuals, sow some in autumn to overwinter. A centaurea, for example, will look more like a 4foot tall shrub with many, many stems from a single plant. Autumn sowing is not just about blooming a couple of weeks earlier. In a temperate zone, annuals which have fulfilled their expected lifecycle (ie, dropped seed which germinates the same season and grows on all winter) are truly astounding. Also applies to semi-hardy annuals sown in spring - the root size is determined by the amount of space in the growing medium...so a larger pot (or the largest of all, the ground) will allow for significant differences in size and vigour.

Yea, if you want instant/quick impact, buy the bigger size. Although the 6-packs that I buy aren't that small -- it's the traditional 4-pack that flats are traditionally sold in that are comparatively tiny. But, the cost difference can be significant. I don't plant much in the way of annuals in the ground anymore, most of my stuff is in pots or used as larger accents in the ground (a good-sized Black & Blue salvia, for example), so I tend to buy the larger sizes. Lots of foiks still "bed out", though -- so the cost of even larger-size 6-packs would be prohibitive. I know a lot of folks in warmer zones/more temperate areas may not be able to understand, but up here in the north summer is all about color -- we only have 3 - 4 months of prime annual growing season, so we go all out and get that show on the road because it certainly isn't going to last long.

@Campanula, I'm curious about your saying that autumn sowing lets annuals develop and bloom earlier, can you explain a bit more please?

Are you referring to direct sowing outdoors (as opposed to...sowing indoors and growing under lights through the winter)? Also, what is "a couple weeks earlier" in contrast to - seeds directly sown outdoors in spring?

Last year, was the 1st and last time I tried sowing on my own. It was a similar experiment in knowing I would be planting fairly fully established big rootball sized annuals. LOL, I've got like $1600 worth of LED grow lights - ahem, the stuff that the mary-j-wayne growers use sitting around these days.

It was just too much ~work~ sowing/growing myself. I'll leave it up to the growers and the nurseries for my sales ;-)