I completely agree! I love HOT and BURNT colors like HOT Pink or Burnt Orange. Talk to your florist about colors, or go to your local hardware/paint store and look at the colors available that would match the yellow you are using...and see what catches your eye first! Best of Luck!
In my experience, it's a great idea to pick a color w/ "pop". Since white & yellow are generally seen by the eye as light/neutral, lavender would, potentially, give the wedding a Necco Wafer palette: all pale & chalky. Don't let this count out the purple! Rather, think "violet" or "plum" or "deep lilac", in small accenting amounts; like jewels in a crown! Plus, it's easier to find flowers (iris, stock, tulips, lisianthus, heather, statis, slavia) in these richer, brighter tones. Best of luck!