Does it make sense to buy a Quadro or FirePro GPU?

Do these cards really speedup animation playback in the viewport or can you get away buying a cheaper Geforce or Radeon GPU?

In other words: Is it worth the investment? -> These things are power consumption hogs everyone knows that. What is the best GPU for under 400 or 500 USD?

It's the age-old dilemma and I cannot really help you there, because I am facing it myself ATM. The "pro cards" versus "gamer cards" debate will probably never be fully settled. One reads reports of people running a decent "gamer card" without a glitch, while others claim to have ditched the "gamer cards" altogether due to severe problems they were experiencing. (Search the Mailing List Archives for instance, for a taste of the diverging views)
The only thing I have picked up over the years (but even this info might just as well be outdated too), is that many people have reported problems with ATI cards and its drivers, more so than on the Nvidia side of things. I couldn't give you any authoritative statistics, but this is based on the impression I got from years of forum surfing.
My own attempts at deciding which card is best for me, have led me to believe that (on my budget) the Quadro 2000 might be a nice solution. But buying a suitable graphics card for Softimage seems to forever remain a leap of faith IMHO and in the end every user must in the end leap on his/her own...

I'm from the "I bought a gamingcard and it works very nicely"-group, and also every workstation I ever worked on had gaming gpus installed on them without any hiccups. I can therefore very much recommend buying a nice 500 dollar gaming-card, which should give you pretty much the same performance as one that costs about 6 times as much.

Nobody can guarantee that it will work flawlessly, but it's pretty darn likely that it will.

Put my signature under Leo's post. I agree with everything he said.

As far as I know there's not much difference between gaming and pro cards. They are all based on the same architecture. Pro cards have more RAM, different drivers and ridiculous price tags. It's quite simple: you charge as much as you can get away with. The general public and gamers don't spend thousands of dollars on a GPU. Businesses do.

Look at Adobe Premiere CS5. Officially, the GPU acceleration is only compatible with quadro cards. But of course it works great on gaming cards.

I'm convinced that companies like Autodesk and Adobe get *something* for recommending and even implying you need "pro" graphics cards, and I think it's one of the biggest myths in all of the 3D world.
I recently bought a GTX 460 with 2 GB of RAM: http://www.newegg.com/Product/Product.aspx?Item=N82E16814130611
And it works just great in Softimage 2012. Then again, my "old" GTX 285 was working great too, but it only had 1 GB of video RAM.
If it were only Softimage I was using I would have waited for the prices to come down a little until I could get a 500 series with 2 GB, but I needed something with more Vram right away since my Mudbox scenes are becoming more complex and RAM-hungry.
Now when you get into bigger and more complex scenes, the Quadros may begin to make a difference, when it comes to RAM, but when it comes to performance the difference is much less.
Of course, the official line is they can't support the myriad of gamer card varieties out there, and it's easier to test with and support the pro workstation cards, and there's probably a certain amount of truth to that, but at the same time they know that a whole lot of their customers are successfully using the GTX line and other gamer cards with their products.
For that matter, if they say they don't support your video card it's easier for them to deny you support if you have a video-related problem...

I also think Nvidia and their manufacturers are not being very smart about their pricing. They could sell those "pro" cards for half the price they are and probably sell twice as many or more and make up for it. I doubt it actually costs them any more to make a Quadro than it does a GTX, certainly not 4 times the cost. But that Quadro name on it is really all you're paying for.
Just my .02.

I have been using "gamer cards" for years with no problems that I could discern. They talk about Quadros rendering the on screen wireframe better, but I really dont see it myself.
I am gearing up for a new rig and have been wondering about this too, I asked a workstation supplier if they could do a rig with a game card and would it make a difference, all that said was that they couldn't then certify the rig as a professional workstation, but I really dont see what that is actually supposed to mean anyway compared to a top end game box with the same processor etc. I figured that like the Quadro it was all just marketing speak.

I have both, a quadro m2700 with 512 mb on my laptop dell (core duo 2 t9600 and 6gb ram) and a GTX460 1gb on my workstation (phenom x6 1090 and 16 gb ram). my laptop and my workstation can move the exactly polygons number and my old (and mobile) quadro perform exactly like the most new and (on paper) most power GTX 460.

If I use software like octane or blender cycles (gpu based renders) GTX460 is more fast and perform better then my quadro