Also, yea from the looks of it, Sanji is apparently down for the moment, but i wouldnt count him out. HE has had battles in the sea train, but compared to the CP9 what were Wanze and Jerry exactly? Nothing. If Sanji is going to be considered a threat just like the other members of the SH he has to have his own part in taking down one of the CP9.
Franky and Zoro took out guys from the sea train too, but theyr fighting CP9 atm. Franky is fighting one of them solo.
I don't think its about power in this case. Its about ever-changing circumstances. Sanji was the first "free" Strawhat (not counting Robin, who was being watched by Cipher Pol, or Ussop and Franky, who were captured) to fight on the train. He made his way past Jerry and other Cipher Pol and Marines in order to even free Ussop and Franky, then ended up in a "chef battle" with Wazne while Sogeking went for Robin and Franky took on Nero up on the roof. But while the Wazne fight lead to him fighting and eventually gaining victory (both in being a warrior and a chef), Calipha is a completely different opponent. While she is CP9, she's also a woman (and a sexy one at that) and has an unknown DF. While it is unknown whether he's actually out of it for the moment, he's down due to his gentleman/pervert ways conflicting with her flaunting/feminist ways. While he probably could take her or several other CP9 members, he drew his weakness and will either fall or rise due to it. And if he stays down, then its less because of Sanji and more because Oda wants to show off the other SH with Sanji getting as much exposure and battle time back on the Sea Train.