They will all support two monitors (it's the graphics card that will determine that). You might want to support three monitors, and also many use HDMI now (monitors that is), so that's something to consider if you intend on buying a screen in the near future.
Careful of HDMI for PCs. I got a new grpahics card yesterday and it only had one DVI port, with an HDMI port. This annoyed me, but luckily I have a Sky box I don't use so took the HDMI cable from that. Picture was shit, even though I've watched Sky on that monitor via HDMI.
Turns out that (undocumented in the manual or anywhere else) my monitor doesn't support PC input via HDMI. Had to use an HDMI>DVI adaptor.
HDMI is only DVI plus sound so entirely unnecessary for PCs where you're probably outputting the sound separately through speakers.