The proprietary drivers have worked OK for me, but I've had issues with playing video. I just couldn't get smooth framerates. The radeon driver was worse in that aspect. I swapped in two nvidia cards and video looked much better. It should be fine for general use and I'm still trying to make the ATI setup work. I don't need 3D, just video.

I have a 5870 eyefinity 6 that has 6 display ports, but those are no longer made and expensive (and overkill).

I found a $60 Radeon HD 6450 card made by Sapphire on Newegg (N82E16814102960) that has two dvi and one displayport, that should work for three monitors. There are other options as well of course, just make sure the cards are advertised as supporting eyefinity and they have at least one displayport adapter. I've had success with an Accel active displayport to DVI adapters.

Thanks....I may try an AMD. I don't need 3D support either, but I do need compositing support (does no 3D mean no compositing? Not sure...).

Not having compositing on the linux desktop these days means you're a second class season. Both Unity and Gnome3 require it to function...if you don't have it, you have to fall back to Unity2D (incomplete user experience) or Gnome 2 (no longer supported. KDE actually does the best of the bunch when it comes to Xinerama so far, but I really prefer Unity or Gnome3.

I've read that if you buy two similar Nvidia cards (same GPUs), you can get compositing across three monitors, but I've not spoken with anyone who can verify. If anyone reading this can, please provide your vid card model.

Do you know if this Radeon HD 6450 will support compositing across three monitors? $60 is cheap to me to get this.

Thanks!

I'm currently using a NVIDIA GT218 (for one monitor) and a GT520 (for two other monitors) on my Arch Linux system. Although Xinerama support is nearly unusable with this setup (most likely due to the different chipsets on the cards), you can do TwinView (for two monitors) and a separate X screen (for the third) or 3 separate xscreens. I just do 3 separate xscreens (I'm a gamer and don't like to see my quake client stretched across two of my monitors and my TV :) ). You can't move windows between monitors with Xinerama or TwinView, but that's a sacrifice I was willing to make for my configuration. I am able to do compositing across all three of my monitors with this configuration.

Anyway, I hope this helps!

That's useful to know.

It looks like that specific card won't work for three monitors, because output #3 is hdmi and not displayport.

Actually, the N82E16814102960 is dual-link DVI + DVI + HDMI.