Be careful with marketing claims.
166x ... 150x ... it's been shown with DSLRs that a manufacturer's claims for rated speed is not all what it's cracked up to be.
The Sandisk Extreme 3 is rated at a minimum 20mb/s read and write which is damn fast. Lifetime warranty.
The Transcend 150x card is supposed to go "up" to 150x but only a 5 year warranty.
The Kingston Ultimate 133x card is claimed from their website to be "23mb/s read, 20 mb/s write" ... I don't know what to make of their claims. Lifetime warranty. I do have quite a few Kingston products. 2x512mb regular CF and 2x1gb Elite Pro SD and have had no issues whatsoever. Would definitely buy them again.
There are others like Corsair etc ...
I'd go to an Axim-specific site like
www.aximsite.com and ask questions there. Don't know whether the Ax can sustain such high read/write speeds which would take advantage of high-end cards. I haven't done any testing with my Elite Pro cards yet. I'm still playing around with my x51v at the moment.
Getting a card that's faster than what the Axim can do would be a waste of time and money though.
Hope that helps.