*sighs* while you can get away with using game cards - I wouldn't on NVidia side as their newer series have most of Quadro side stripped out; while AMD hasn't stripped their cards out.
Also drivers do make a difference as Nvidia and AMD put hooks into their pro lines that run things a lot faster. You also have a lot less compatibility issues on pro side as they've been certified to run with these programs.
Now k2200 is a solid card but also ranging from 550-650 pounds.
M2000 is a little faster with slightly more cuda cores as its refresh to replace the k2200 - depending on where you go; either can be found just under 500
AMD's Firepro -
W5100 is a very solid card for the price - its faster than k2200 and is cheaper; its also faster than m2000 - and cheaper
now the beast w7100 - I've seen it low as 350 at least one place but normally its about 550+ but its massive upgrade over k2200 as its next class card which normally goes against K4200 and now m4000
Honestly - sweet spot at 300 is Firepro w5100....but the one stand out if you can actually get it at 350 and its w7100 as its a beast of a pro card; but honestly I'm not sure if that's new or refurbed.
I've bought a lot of these cards for my engineers in my old job - both Quadros and Firepros - unless you can get a steal on Quadro - no real reason pick one over firepros - they tend to be a little cheaper and faster in their price ranges.
but either w5100 or m2000 will be your best bet - I'd go for the cheaper one

which from my looking around is the w5100