Shuttle have 3 good models that would suit.
SZ68R5 - Based on the Z68 express chipset - Available now and works very well and can run IB or SB with the latest bios
SZ77R5 - Based on the Z77 express chipset - Due into the UK very soon. I have not had a chance to test this yet, but expect little difference to the Z68
SX79R5 - Based on the X79 express chipset and for SB-E LGA 2011 - Available now. More expensive than above but can support hex core.
If you are looking to overclock then all Shuttles need Bios modifications as they restrict the maximum power for sustained periods. IB looks like a bad choice, to me - from what I have read - if you wish to overclock. If you are sticking at or near stock then they are all excellent. The SX79R5 is only better if running applications that will use the extra cores. For games the SX68R5 or SZ77R5 will be just as good as the SX79R5 and quite a bit cheaper.