There's no need for a new monitor. I have a 1440x900 monitor as well, but with Nvidia you can use Dynamic Super Resolution (DSR) which lets you use a 4 times bigger resolution, in both our cases it's 2880x1800 which well surpasses 1080p and 1440p. Then about recording and streaming, AMD have those softwares only because Nvidia had them before AMD, which are Nvidia Share (the old Nvidia Shadowplay), and streaming software. With both of those I've been able to record a CS:S clip
with no performance issues (no fps drops at all whatsoever, unlike Fraps).
It doesn't matter if you don't use light styles because other people does and you'd suffer fps issues anyway, also because the flashlight causes some problems too, and that's irrelevant because it's a game feature, not a map feature.
Just to make it clear, I went from an ATi Radeon HD 5870 to an Nvidia Geforce GTX 560 Ti, both are pretty similar in power, but I gained a lot more performance on both Goldsource and CryEngine based games with the 560 Ti. Respectively, ~100+ fps on Goldsource and ~20/30+ fps on CryEngine.
Also, CryEngine based games runs better on Nvidia chipsets; going from Far Cry 1 to Crysis 3.
Basically, you can start thinking that there's no particular difference in Nvidia and AMD cards only if you play modern games (2013 and above). But still, some modern games suffer from performance issues with AMD, giving Nvidia the lead anyway.
It's not about being an Nvidia fanboy, it's about matter of facts.
The only thing about Nvidia is that their drivers are a bit less stable than AMD ones. That's it.
Then the choice is yours, I'm just trying to point you in the right direction. I've based myself on my personal experiences and overall people experiences, since Nvidia owns like 70% of the market as far as I know.
Cheers for the map though. :3