Natalie - it's great that you've got the opportunity to buy a new clarinet, but DON'T just order one - that really isn't what you should do, now that you are more advanced as a player!
You should go to a shop which has a good selection of different brands of clarinet (the 'Big 4' brands are Buffet, Leblanc, Selmer and Yamaha). Take your usual mouthpiece with you, and try out lots of instruments there (most music shops have somewhere where you can test out instruments).
Take a friend/teacher with you, who can listen to you play on the different clarinets and give you their opinion - but if it's your teacher, bear in mind that you should offer to pay for her time (even if she doesn't accept, she will be pleased that you offered!).
Take a tuning meter too, and a couple of favourite pieces - perhaps a slowish, lyrical one and a faster, more technical one - to play on each clarinet, to see how they respond.
Even two clarinets of the same brand and model will vary slightly, which is why you really should try-before-you-buy, so that you get what is best for you!
I've bought a lot of my clarinets from eBay, where generally you don't get the chance to try them out - by being careful I've come out of it with some excellent second-hand instruments at a very good price. But if you're buying a new clarinet, do make the most of the chance to test-run anything you're interested in!
Hope this helps,
Jo
PS The Leblanc Opus clarinets are VERY nice - but, unfortunately, very expensive too!