Actually I personally think that for the price difference you pay for a brilliant rose/destinee/etc (ie, diamonds that are cut with more facets than the usual 56facets), you can choose a diamond which is a better colour and clarity, which will give you a greater brilliance. You might even be able to get a larger sized normal diamond. I feel it is important to select a diamond which is considered a "perfect cut" - ie, the dimensions are a certain ratio/proportion.
My diamond is a 1.15ct G colour VVS1 round brilliant perfect cut, 56 facet diamond. I chose it over a smaller size destinee diamond, paid a whole lot less (and got a better clarity too), but everytime I wear it people remark about its shine and brilliance.
Shop around a lot. Bear in mind that Love & Co, Lee Hwa, Gold Heart and Aspial are actually the same "mother" company. Good luck!