You made the right choice for CPU.. I am also having core i5 2500k..
For motherboard, any z68 chipset montherboards will do... z68 have feature like Smart Response Technology (SSD Caching) which make it worthy..
Don't go for Intel DZ68DB, they have only one PCI-e x16 port... Buy motherboard having atleast 2 x16 PCI-e ports so u can use crossfire/sli...
Motherboard brands doesn't matter, it can make only very little difference in performance... I think MSI will be good in performance and budget..
Make sure motherboard provides good spacing between expansion slots, also enough gap between motherboard and RAM..
I have MSI Radeon 6950 Twin Frozr III card, so it take lots of space for graphics card...