The link that you are refering to shows what ios have what default spe firmware bundled with it. But you can mix and match the firmware for SPEs with ios.
So you can load 12.2(2)XB7 OR 12.2(2)XB10 (or XB11 once its released) and upgrade the spe firmware to 7.18.3 seperately if you want.
So in other words, spe firmware is seperately upgradable.
Visit following link for that
http://www.cisco.com/en/US/tech/tk801/tk36/technologies_tech_note09186a0080094859.shtml