Don't you even bother looking at the specifications before buying a motherboard ?
The Intel website has a nice page for every motherboard they produce that tells you everything about it, including the number of PCI and memory slots, and there's also a nice picture of the board.
You can also download the user manual and technical specification before buying it.
Buying a board just by looking at the name "DX58SO" doesn't seem like a good idea to me.
Of course I look at the specifications. And I read reviews. The reviews are never great on Intel boards because other boards offer more bells and whistles. The only reason I have stuck with Intel is because they are a stable board and that is important to me for the business I'm in. And by the way, when you are looking through specifications you don't look to see if it supports USB 2.0 or if it has onboard ethernet. Those are a given. You will scan the specs and acknowledge they are there. The fact that the previous extreme board had 3 PCI-E slots and when I scanned the specs of their current board I read the following:
- One primary PCI Express* 2.0 x16 (electrical x16) bus add-in card connector
- One secondary PCI Express 2.0 x16 (electrical x16) bus add-in card connector
- One PCI Express* 1.0a x16 (electrical x4) bus add-in card connector
I interpreted that as the board having 3 PCI-E slots.