I adore my Dyson, and we're hard on vacuums also. (Four kids 7 and under; carpet in the eating area, three cats, we vacuum at least every day.)
Here's the deal with the colors - the colors tell you which attachments package it comes with, but there is no difference in the actual vacuum. For my needs I found that the red package ("Low-Floor Model"is the best, though what I actually did was buy a yellow one and then buy the low-floor attachment, but it's as if I bought the red one, if that makes sense The low-floor tool is fabulous and basically turns the vacuum into the equivalent of a canister. It allows you to clean hard floors very easily. I vacuum my hallway and kitchen with it, and use the regular upright mode for our living room, dining room, and playroom carpets.
I got a refurbished one via Amazon.com because it was cheapest, and I've been very happy with it and also with Dyson's customer service. There are a number of little parts that disconnect so you can unclog it yourself if you suck something up that sticks...it takes a little getting used to, but I'm feeling really competent about troubleshooting it now. If the suction gets weak it's just about always because something is stuck somewhere along the line (I suck up too-big things sometimes too). But it's really easy to fix. I love that the 800# is printed on the side of it (LOL)...I've only used it once but it makes me feel secure.
I am pretty frugal and I felt it was worth the $$. I paid about $360 for mine total, the yellow model with the separate low-floor attachment and shipping.
Amanda, mom to Everest (12), Alden (10-1/2), Ellery (7-1/2), & Avery (6)