10-speed shifters will work with 9-speed derailleurs and chainrings and cassettes just fine when you use the alternate cable routing to the rear derailleur. See:
http://www.ctc.org.uk/desktopdefault.aspx?tabid=3946 and
http://sheldonbrown.com/derailer-adjustment.html
I've been doing it for about a year now, using a 9-speed Ultegra drivetrain and 10-speed Microshift shifters. I just make sure the last click is disabled by the inner limit screw on the derailleur to keep the derailleur from going into the spokes!
Then, when you want to buy a new chain and cassette, you can convert to 10-speed any time in the future, changing back to the normal cable routing.
But you might just need adjustment-- Can you get the shifter to click 8 times just pulling on the cable by hand? If so, then it's probably just time to adjust everything, and not bother with the 10-speed replacement yet.