Just wanted to share my experience on the front I/O panel.
Wanted to buy a new case (Cosmos II ?) for building my new rig, the only reason being the ATCS 840 doesn't have USB 3.0 on the pop-up front panel and that is a bit stupid in my opinion (buying a new case just for that reason)
USB 3.0 drive bay panels are available of course but the pop-up panel is really nice and the case is the best I've seen even today.
So after several hours searching the Internet and having disassembled the pop-pop panel, here is the simplest option I found : 2 USB 3.0 A Male / A Female cables connected on one side to the motherboard with a 20 pin adapter / 2 USB A Female.http://www.ldlc.com/fiche/PB00121229.htmlhttp://www.ldlc.com/fiche/PB00121229.html
Now on the other side (connecting to the front panel), it's more frustrating...
If you like to solder you can buy a dual USB 3.0 header like this :http://www.conrad.fr/connecteur_usb_30_9_poles_p_61607_61607_887767_967845
Solder off the dual USB 2.0 header from the PCB, solder on the USB 3.0 header and solder 18 pins (or make yourself a new PCB).
A more simple option is to solder off the USB 2.0 (or cut it off) and just glue the two female ends of the UBS 3.0 cables (one end on top of each other, some plastic needs to be cut off to get flush with the cutoff).
Case is for upgrading existing rig, going to buy Asus Z9PE-D8 WS Mobo (EVGA SR-X is HPTX format, shouldn't fit in ATCS 840 ?).
Mobo mounting holes (EEB) are not all the same as EATX (ATCS 840) but you can drill missing holes if needed :http://www.tomshardware.co.uk/forum/258406-12-eatx-interchangable
Will also upgrade the water cooling (2 CPU Xeon E5-2687W, 2 EVGA GTX 680 Hydro Copper).
3 x120 cm radiator will be mounted under the top panel just under three 120 cm fans.
Planning on getting 32 GB memory (GSkill DDR3-2133 PC3 17000, Asus website says Z9PE-D8 WS supports 2133 OC).
Storage is not upgraded (bought last year) : LSI MegaRAID 9265-8i + RAID-0 4x OCZ Vertex 3 Max IOPS 240 Go (DATA) + RAID-0 4x Corsair Force Series GT 60 Go (System).
Will see how all this OCs, given E5 limitations ?