i LOVE MAC eyeshadows because they are sooo pigmented. they also have fantastic colors that's just fun!!!
My sister had her make up for her high school prom (8 years ago) done at Chanel, and it was soo beautiful. Chanel is just... luxurious.. hahahaha!!
(but in all honesty, even though Chanel/Dior/etc. make up is super expensive, it's a way of owning something from them when you can't afford their bags and clothes.. heehee)
Chanel...I had a friend who was a MA for them and she always used their stuff to make me up! I have a bottle of No. 5 that was my grandmother's from YEARS ago. I'll always keep it even though I may never wear it....or maybe I will
I love MAC soooo much. TG is right; they are super-pigmented and the color stays true. The only thing I would say about MAC is that they tend to do super intense/dramatic eyes, so you would have to be clear about what you wanted. I went once to try out greens and when the girl was done I had bright green eyeshadow up to my eyebrows... not quite the look I was going for. So just be sure to say that you're looking for a new look for a wedding.
Or you could go to a Sephora and talk with a MA there and you could discuss together what brand might be best for what you're looking for; they have so many brands there. Nars is also amazing.