The mini tower is the largest one the have.
Its goes Mini Tower (Has two DVD Drive bays, full height expansion slots, 2 3.5 hard drive support. Then it goes the Desktop which is the same height but half the width and uses a full size DVD drive. Then the SFF is a bit shorter and half width, then they have the USFF which is even smaller.
They also have the Micro now that replaces the USFF which has no DVD drive and is around the same size as the Wii
Now ever since the Core i Series you have been able to use BOTH the onboard AND addin card. The 9010 can take up to 2 cards if need be. Now the 9010 I don't think has any extra PCIe 6 Pin Connectors so video cards are limited to 75 watt each. Also depending on the wattage of the PSU it may only have enough power for 1 card. Their are some GTX 750Ti's that don't require extra power.
Now with the 9010 YOU CAN add in ANY standard ATX power supply. The only thing is you WILL want to get a 90 Degree adapter for the hard drives as a normal connector won't work. You would need the following.
http://g01.a.alicdn.com/kf/HTB10LZoKXXXXXcoXXXXq6xXFXXXJ/2pcs-lot-hot-font-b-SATA-b-font-15-Pin-Male-to-2-font-b-SATA.jpg
Now if you want to use both you have to go into the BIOS and make sure Multi Display is enabled (By default it is). Also note that the Onboard, if anything is connected to it, will be the primary video card so there should be another section to make it the PCIe card the primary if you plan on doing anything like gaming etc on it. If it is just to add more monitors then it doesn't matter.
If you don't plan on using the onboard, just plug everything into the video card. The onboard video card will NOT be enabled or be able to use unless you connect a display to it and restart the PC. If it detects their is no display on the Onboard it won't even enable it.