I still remember reaching the 200k mark, and now that you've got up to 1 million is just crazy. However, it was about time all those days would pay off.
I've got a Z11 and it has 290mm, and with that PSU you MUST get the 7870 XT with Boost, maybe from ebay for a good price, considering is performs as well as a 660Ti, which is in a different price range.
Forgot to ask you : what case do you have? ( it's important because a huge GPU may not fit inside ) and what PSU? ( the 7870 needs some juice to get powered up )
How much are you willing to spend?
With some OC to the CPU, you could go for a Sapphire Radeon HD 7870 XT With Boost ( Tahiti LE chip, like the one on 7950): http://www.sapphiretech.com/presentation/product/?cid=1&gid=3&sgid=1160&pid=1790&lid=1
In that price range, there's no need for you to consider buying a TN panel monitor. You must go for an IPS or at least VA ( TN is a big no-no). And the GTG response time doesn't matter that much when you're talking about ~5ms or less.
The MX239H is very good at image quality, especially because it has an AH-IPS.
A very decent monitor with VA panel is the BenQ GW2750HM: http://www.benq.com/product/monitor/gw2750hm
I hope it helps :)