Hi Adam,
I have exactly the same laptop, core 2 duo, 8gigs of ram, and the 256mb graphics card.
I have updated to mavericks and FCPX 10.1
Not only does this new version work fine, but I have to report (and I am surprised by this) that FCPX 10.1 creates optimized media twice as fast as it use to.
FCPX 10.0.9 took 6 mins to create an optimized ProRes clip from an h264 mp4 file of about the same duration.
Mpeg Streamclip (the previous gold standard on my machine) took 5 mins to create a ProRes Quicktime.
But FCPX 10.1 has just achieved the same transcode of the same file in 3 mins!
So even on aging laptops like ours, there are dramatic gains to be had if you upgrade.
Plus Libraries are so much better to hold events and projects in!