Severus

No matter what vacuum you buy, maintenance will always be required especially in situations such as you have described.  There is no way around it.  Were I you, I'd look for a machine that allows for easy access to the belt and brush roll to make it feel less of a chore. 

Being a fan of bagged vacuums I'd want the biggest disposable bag available to me.  As for canister or upright, if you're not fond of canisters you're probably never going to be and what's wrong with that especially if you're main interest is carpet cleaning?  Consider a simple machine like one of the Sanitaire standard uprights.  Check with the dealer regarding high-filtration bags. However, these machines won't do you much good above the floor.  See link --http://www.sanitairevac.com/professional/products/cat_upright.html

If durability is a serious issue and weight concerns don't bother you much, check the "re-built" thread.  Kirby (G5 and up) -- an upright I like and own but would be hesitant to recommend that anyone buy one brand new -- allows easy detachment of its rug cleaning head and you can snip away hair and the like with not too much problem.  They also can be used with a very good high-filtration disposable bag that is generous in size.  They are heavy and a bit bulky but the models mentioned do have transmissions that make pushing and maneuvering the machine relatively easy. Please note that they are not great if you want to clean under your bed or low furniture.  Noetheless, properly adjusted for carpet height they should give you good service.

You should be able to land one from a reputable seller on eBay (always review selller feedback) for roughly $250 to $400.  These usually come with a slew of tools including a rug shampooer that most folks will never use but, hey, what are closets for?

Good luck,

Venson