The motherboard only has lanes provided by the CPU, a 4770k has 16 lanes
As an example nvidia cards run x16 if its one card and x8 if its in sli so 2 nvidia cards would turn the other lanes off
You cards an ati which I believe can run at x8 or x4 but I'm not sure there
GPU should always go into the highest spot it can go so the very top x16 pcie plug is where your GPU should go
Can you fit the raidr in the x1 slot above the graphics card?
If you look in your manual page 1-26 it shows which PCIe lanes are shared across which pcie slots
As for setting up a crossfire, even if it was possible with the Raidr still installed you'd be pushing your power supply, especially if you planned to overclock
290x cards according to toms hardware power consumption charts under load use 300-400w, so 2 with load would be 600-800w, an over clocked 4770k uses 130w easy possibly more due to how much ram you have installed, that's already 730-930w without adding in the Raidr, ssd, optical drives, any addition hard drives etc. etc.
If worst came to worst you could always see about returning the Raidr, the research I did building my rig showed the Raidr is actually slower then 2 ssds in raid
CoolerMaster HAF 932 Advanced/ Maximus VI Formula/ I7-4770K/Swiftech H320/ Corsair HX850/ G.Skill Trident X (2x8) 16gb 2400MHz/ 2x 840 EVO 120gb(Raid 0)/ WD 1TB HDD (Backup/Storage)/ EVGA GTX 1gb 560 TI/ Asus 12x bluray combo