Hello... Q9650 the Q9550 will be cheaper on EBAY... http://www.asus.com/Motherboards/P5KPLCM/HelpDesk_CPU/
Q9550 is true Quad core CPU http://www.cpubenchmark.net/cpu_lookup.php?cpu=Intel+Core2+Quad+Q9550+%40+2.83GHz it can be just as fast or better than current i3's Your next upgrade step would be a i5, MB and DDR3 memory... $$$ I know.
The Core 2 Quad Q9xxx cpus will fit and would be a big upgrade, but even they are still old. You're probably better off upgrading your mobo too and getting something new.
Hello... Q9650 the Q9550 will be cheaper on EBAY... http://www.asus.com/Motherboards/P5KPLCM/HelpDesk_CPU/
Q9550 is true Quad core CPU http://www.cpubenchmark.net/cpu_lookup.php?cpu=Intel+Core2+Quad+Q9550+%40+2.83GHz it can be just as fast or better than current i3's Your next upgrade step would be a i5, MB and DDR3 memory... $$$ I know.