I'm looking to build a new box driving 3 displays @ 1920x1080, full color - probably using the Asus Sabertooth 990FX R2.0 motherboard. The monitors I'm looking at (Samsung S22A300B) have DVI and VGA input (no HDMI). (I may have another output running to HDMI input of a TV - to stream digital movies occassionally.) I intend to run Ubuntu 12.04 LTS, hosting VirtualBox guests - Windows 7/8 and Linux (primarily Ubuntu). I want to run HD (blu-ray, upsampled DVD, or digital copy) video from any of the virtual guests (although not simultaneously), but, in general, I'm not a demanding display user - no gaming, productivity/programming software only. I would like to use the latest UI effects in Ubuntu and Windows, however.
I'm looking at the Radeon HD 7750 card (or maybe 2, if necessary). Is 1GB VRAM sufficient? Should I go with a more expensive card, based on the 7950, perhaps? Or is there something even better suited to my needs? I know that cards beyond the 7750 generally run hotter and require a separate power connection, and I'd prefer to avoid that, if possible. Is there any single slot card that can do the job? (My understanding is that these cards generally take up 2 slots due to thickness arising from the incorporated fan.)
I am not particularly familiar with the HD 7750 series of cards, but if the particular card you're looking at has the outputs for your monitors, then you should be in business. Yes, the 1GB will be sufficient for normal productivity usage and you'll be able to handle all of the Ubuntu UI effects with a 7750.
According to Tom's (http://www.tomshardware.com/reviews/gaming-graphics-car...) the HD 7750 is the best card you can get without additional power, so if your power supply has additional PCIe power adapters, then you can get into much more powerful cards. The 7950 you mentioned is in an entirely different league than a lowly 7750, it'll do eyefinity gaming just fine.
I don't think I need the "eyefinity" - I'm not looking to make one seamless desktop for gaming purposes. Rather, my intention is to have each display present a full screen virtual machine (guest) session.
The 7850 seems reasonable to me; it has all 4 output connectors, too. I'm not wild about the power requirements, but it's not that critical. And if it allows me to stream video to my TV and keep my son occupied while I can do some work or watch something else on one of my screens, well, all the better. Still only 1gb RAM, but I understand that should be sufficient if I'm not gaming.
This is the wrong forum to really get into the details of mobo/cpu choices, but here's a brief glimpse into my thinking...
I do multithreaded / multiprocess software development, so I am looking for inexpensive cores. AMD Bulldozer FX8xxx fits the bill - it's not perfect, but it's more active threads on a budget. (Maybe the 6-core Phenom II is better, so I may go with that instead, especially since I'm actually virtualizing, which would probably benefit from "full" cores.) Anyway, given that I need an AM3/AM3+ socket for the CPU + the FX990 chipset, well, I came to the Sabertooth mobo based on this review: http://www.tomshardware.com/reviews/sabertooth-990fx-99...
I know the review is 1+ year old, but it seemed reasonable. Honestly, I haven't seen much real data (positive or negative) about the "thermal armor" on the board, but it would seem to be a real problem if it's actually working opposite of what was intended!
If I had more money, I'd definitely opt for the Intel i7 with Sandy(Ivy)Bridge - it's a very good architecture - better IPC, and has less shared resources / fewer bottlenecks than AMD's BD architecture. I'd love to play around with Hyperthreading, too. But it's expensive (relative to AMD). *sigh*