Looking for a good external hard drive

Name says it all really I'm looking for a pretty good hard drive in the capacity range of 320 Gb to 640 Gb No more no less (unless more ends up being less then less is). My budget is 125$ CDN I've been looking around both newegg and NCIX but any retailer is good in the end (long as they take Paypal. Here are some of the ones I've been looking at:

Western Digital Elements Desktop WDE1UBK6400N 640GB USB 2.0 Black External Hard Drive - $99.99
http://www.newegg.ca/Product/Produ [...] 6822136324


Seagate FreeAgent Desk 500GB External Hard Drive Silver 7200RPM USB2.0 - $99.99
http://www.ncix.com/products/index [...] e%20Retail

Acom Data Puredrive 640GB 7200RPM USB 2.0 eSATA External 3.5IN Hard Drive - $119.99 After Mail In Rebate: $94.99 CAD
http://www.ncix.com/products/index [...] Com%20Data

Buffalo DriveStation TurboUSB with Power Saving Mode 500GB External Hard Drive USB 2.0 - $89.99
http://www.ncix.com/products/index [...] omoid=1006

esata or any other isn't necessary as none of my computers have it and I'd be dishing out the needed moolah to make it USB 3.0 compatible (which I think means just needing to get a new enclosure, might be wrong)

Thanks in advance for the help!