Should be able to. I've been using 9spd front and rear mechs with a 7spd set up for 2 years trouble free (Deore front, LX rear) and 9sd chain rings too (FSAs) for 6 months.
Lovely! Cheers for that! I'm currently running a Deore 8 speed setup at the back and wanted to make sure. I'm going to upgrade to 9 speed SRAM X.9 over the summer (when I can afford to!!), but I didn't want to wait until August before I got back out on my bike.