I need my readers' help: vacuums

Okay, trusted and faithful internet peoples: I need a new vacuum. Our Hoover upright Windtunnel has served us well since we were married, which makes it about 12 years old. There is not really anything wrong with it, except that when you pick it up and set it back down, dust escapes out the top and the filters are worn out and even after cleaning seem terribly dirty. My main problem is that it is heavy and bulky and at the moment, it has to live in the garage. (Downfall to living in a very small house with no closet space - there is no where to put a vacuum!) Mr. Burli thinks we spent about $200 on it when we bought it (I don't recall it being that much, but I have a feeling we had some wedding gift cards or something), and he thinks it will be best to spend more now rather than less, in order to ensure we get something that lasts a long time again.
So, now I need your help.
Here are some of the vacuums we are considering.
Miele Olympus (about $300)
Kenmore Progressive (also $300)
Okay, so really I haven't found much else I am interested in yet. Maybe the Dyson City?


Here are the criteria:
We have hardwood floors (linoleum in the kitchen, tile in one bath) and a few flat weave rugs, so it doesn't need to suction through super piled carpet.
It needs to be better at containing the dust. I don't mind a bag - our current model is bagless, but that means that when I empty the cup, dust flies everywhere, so bagless is not necessarily good.
It needs to be small and compact so I can try and squeeze it in the bottom of our linen closet or bedroom closet.
It needs to handle dust, legos and cat hair.

Can it clean by itself? That would be a plus (although I imagine a vacuum robot would need to be supplemented by another vacuum? Anyone have a robot they like enough to recommend?)

Price - really I don't want to pay 300, but I suppose if the vacuum lasts a while, it might be worth it.

Any suggestions?