What I really want is a drive that's a notch or two up in reliability. Two drives in fact - one for the PC and one that has USB portability. However, it seems there's an exponential increase in cost for such items. Any comments?
Yes.
What you need to do is differentiate between the infinite number of fancy cases, and the disk drive inside.
If you are buying "drive plus case" for 35.99, then I would be reasonably happy to bet that if you cracked open that case, you would find a cheap and nasty drive sitting inside.
Therefore, what you need to do is :
(a) Find yourself a decent external drive enclosure with the connections you need on it
(b) Source your drive separately and place inside said enclosure
(c) Connect said enclosure to computer and format with built-in operating system tools
(d) Robert is your uncle
In terms of "a drive that's a notch or two up in reliability", what you want to do is:
(a) Go to the website of the major manufacturers (hint: Seagate and Western Digital hold the majority of the market share between them these days, Hitachi also hold reasonable marketshare but they're more high-end drives and will probably be outside your price range).
(b) Go to the "business" section of said website
(c) For backup use, take a look at what they have listed under "Nearline Drives" or "Datacentre Drives" (you could look at "NAS Drives" too, but they tend to be mid-range drives). For day-to-day PC use look at their other drives (although don't go too crazy, no need to look at their mission-critical top-of-the-range 15000rpm models unless you've got the budget !).
(d) Pick one of their high-capacity models that they say is designed for "archiving", "high-end NAS", "content delivery" or such like.
(e) If you feel like it, download the datasheets and compare the specs (especially intended workload limit, MTBF and cache size).
(f) Narrow down your shortlist list by seeing what's in stock on your favourite internet shops....
So basically for backups you'll probably end up with a list that looks something like "Seagate Archive","Seagate Terascale","Western Digital Ae" or "Western Digital Se". All of which will be "a notch or two up in reliability" from the crud normally sold on the high-street to consumers !