Looking for LARGE purple Flowers!

Does anyone have any suggestions as to a LARGE single purple flower that could be used as a centrepiece? Large being 6" or so? I'm contemplating a lily of some sort...daisy's are too small...would prefer to stick with a single stem vs. a bunch.
Any suggestions would help!
Thanks!

 

Clematis is a beautiful flower and some blooms get quite large. Hibiscus (though I have only seen red, yellow, white and orange) would have a large flower. Good luck.

 

Dinner plate dahlias would also be an option, although really dark purples are not easy to find in dahlias. You will see more in the magenta range.

 

Echinacea perhaps? Magnus, I think, is the biggest.

 

I just got a new monarda that might fit the bill...variety "Fireball"...a pinky kind of purple, very nice.

Also, a nice giant Allium head would be great as well.

 

Hydrangea? Sometimes they are purple/blue.

 

A large purple Bearded Iris would be very dramatic.