Maxtor Maxline Plus II 7200 rpm in G4 or externals?

[animal]

In 18 months, I'll upgrade to a G5 or G6, but right now I need more 
space in my G4 400 with an ACARD A Hard PCI Ultra ATA/66 and 2 Hitachi 
120GB hard drives.  I also have two older empty firewire cases (120GB 
or less)

I'm looking at the Maxtor Maxline but they are ATA 133 - does this mean 
they won't work or will work slower with the ATA/66?  (I've stuck to 
Hitachi after incompatibility problems with capturing video from a 
Canon dv camcorder to an internal Western Digital hard drive.)

Or would I be better off buying 2 180GB Hitachi ATA/6's to put into the 
G4?

Thanks for any advice

Lynn