Hi there,
Yes the Z87-DH3P is a good board, there is also these boards in your price range:
MSI Z87 GD65
ASUS Z87 PRO
And the PCI-E slots, one runs at X16 which gives the graphics card full bandwidth and doesn't share it with any other slots, where as the X4 slot shares bandwidth with all the X1 slots (Smaller ones)
For e.g its like one car having a motorway to itself (X16) and then the other one sharing it with other cars (the X4 slot)
Hope this helps!