Graphic card recomendations?

Hardware Hub GPU
1

Hi,  I am in need of updating my GeForce GTX 550 Ti to something different.  I currently have two Asus VS238H-P and would like to add another Asus VS238H-P monitor and I don't think my GeForce GTX 550 Ti supports three monitors. I also would like to add more monitors in the future for the purpose of dedicating a monitor for viewing Desktop, Terminal, VirtualBox, Development, Browser and Security cameras.

I don't know much about graphic cards and would like recommendations. My daily OS of choice is Ubuntu 14.04 LTS and I dual boot between Ubuntu and Windows 7 Ultimate. The card(s) need to work with linux and allow enough video to be delegated for video playback(mainly youtube videos), security camera streaming/playback and Virtual OS(mainly windows7 ultimate) smoothly. I hardly play games, but maybe with a better graphics card and more monitors I may consider playing games.

As far as price and brand, I don't want spend a 1,000+ dollars and brand doesn't matter as long as the graphics card works well with Linux.

Current Setup:

Daily OS: Ubuntu 14.04 LTS

Motherboard: ASUS M5A97

CPU: AMD FX(tm)-6100 Six-Core Processor × 6

GPU: GeForce GTX 550 Ti

Monitors: 2 ASUS VS238H-P 23"

2

Well I always recommend a GTX 980/970 depending on a budget.

3

GTX 970 or R9 290. 

970 is better at 1080p by about 5-15 FPS on average. 1440p they are about the same. $100ish price difference. 

The 980 is IMO, pointless. It is 10 FPS faster than a 970 and costs over $200 more.

4

Budget?

If you're on Linux, an AMD card tends to be a better choice simply because the Nvidia drivers tend to be iffy at best. I'd recommend pretty much any R9 series card, so it all depends on your budget. You can get an R9 270 for about $140, a 270X for about $160, a 280 for $175, or a 280X for 230.