Reliable external drives
You enquire about a reliable external hard drive. This does not exisit .......(just joking)
The brands you mention are fairly well regarded, as is LaCie, for their high end stuff. If you want true security for your data, you have to go to a RAID (redundant array of inexpensive drives). While, contrary to the acronym RAID systems are expensive (though not as expensive as the SCSI ultra 320 drives), they offer the ultimate in fail safe reliabilty with at a minimum two copies of all the information.
You may not want to get the cheapest stuff there is. I made that mistake and it cost me. I had to replace the cheap drive with a good one, after the first failed. Cost= cheap drive + expensive drive, and I could have eliminated the intermediate step.
External enclosures CAN be great. The problem is some cheap ones cut corners and this really hurts either the power supply system or the data transfer system, which will kill in the long run. If you get a good one you can save some $$$$ and end up with a high quality product.