Yeah just like I thought..
Now I'm affraid that your motherboard is problem there..
That is P43 chipset motherboard and those can't push more than 420MHz FSB with a C2Q..
Their FSB OC limit ranges from 400 - 420MHz..
And you should consider your P5P43TD/USB3 a good one for making it to 413MHz with Q9300..
Sorry dude for higher FSB you need a better motherboard like P45 chipset and DDR3 support:
Gigabyte EP45T-USB3P (DDR3)
Asus P5Q3 Deluxe,
Asus P5QC (it has DDR2 and DDR3 support)
Also you should look for these X48 chipset mobos with a DDR3 support:
Asus P5E3 Premium
Asus P5E3 Deluxe
Asus P5E3 Pro
Those DDR3 mobos would be able to push that Q9300 to the maximum..
you will be waiting awhile...saying i3, i5, i7 is akin to saying "ford mustang"...
the 1366 cpu's were the first i7's, then came the 1156 platform, which had i3's,i5's and i7's...now we have the 1155 platform, which again has the same as the 1156...
i'm not sure what seperates i3's and i5's and i5's to i7's, i use to think it was hyperthreading and cache sizes, till i realize there were dual cores in the i3 and i5 line that had hyperthreading, and pretty hefty level 3 caches...i7's definitely seem to be a quad-core+ only segment, where i5's seem to be a mix of dual cores, quad-cores, and dual cores with on-die graphics....i3's seem to be dual cores with on die graphics.
a 600mhz overclock is a GOOD OC, and even being a quadcore you still got a few more years of life left to it before its aging architecture and lower clock speed start effecting its performance over 1ghz OC is reachable but not really the normal, and anything over the 1ghz OC is really an exception