Take this 7870, for example: SAPPHIRE Radeon HD 7870 GHz Edition OC
It has 2 x MiniDP, 1 x DVI, and 1 x HDMI. With only two non-MiniDP ports, I wouldn't be able to use all four for the 3+1 setup?
Would Work! 2 Display via Adapter on MiniDP Port, 1 on DVI and 1 on HDMI (or via HDMi->DVI Adapter)
And how about the XFX Double D FX-787A-CDFC Radeon HD 7870 GHz Edition
It has 2 x MiniDP, 2 x DVI, and 1 xHDMI—three non-MiniDP ports like you mentioned, so I would be able to have my 3+1 setup, correct?
Would also work IF you use 2 Display via Adapter on MiniDP Port, 2 on DVI OR 1 DVI and 1 HDMI !
Is any card manufacturer better than any other?
Is it more about customer support than product quality?
Is any company's products best avoided?
Well, there are "Reference Design" and "Custom design" Graphic cards out there! Reference means AMD designed the card and XFX, Asus, Sapphire or who else just bought the card and put a sticker on them! Custom design means that the Manufacterer designed the card himself! So for example Asus DirectCU II cards, or MSI Lightning Series ! they most of the time use better materials and a different fan. (there are also cards in Reference Design with different Fans! For Example XFX dual dissapation!)
Customer support? You only need that wehen a GPU goes defect! and normaly it shouldn't! so "product quality" only affects Custom design Cards, all refernece design cards are 100% equal to each other!
Uh, "best avoided".... depens on the model, there are better and worse cooler/fans out there. XFX Dual dissapation isn't that good on HD7970 Cards, but might do a good job in HD7870 !
Does the factory OC make a big difference from doing it yourself? (The Sapphire one I linked above is overclocked from 1000/1200 to 1050/1250. I understand the 7870 has a fair amount of room for overclocking.)
The only difference is that 1. This clock is guaranteed! and 2. you dont lose waranty!
IF you overclock yourself you will lose waranty! (but AFAIK they cant prove that you overclocked, and normaly cards don't break from overclocking!)