I'm using an Ergotech stand that will fit up to 26" monitors (using extended arms). [link]
I've only used Acer monitors and have always liked the picture. It's not "top of the line" but looks close to it. I would recommend getting a 120Hz monitor if you do any games or HD video, looks much smoother.
Ergotech does sell a quad monitor mount [link]
Or you could go for a horizontal 3 monitor stand and put the 4th on top with a wall mount.
Got a shot of your desk to share?
I've only used Acer monitors and have always liked the picture. It's not "top of the line" but looks close to it. I would recommend getting a 120Hz monitor if you do any games or HD video, looks much smoother.