I agree, you can easily go for an i5 instead of an i7. You only need an i7, if you have virtualization issues and need all cores, for games a 'normal' quadcore is more than sufficient.
My suggestion: take a i5-3570K
As for the motherboard, if you check
this site, just start by choosing the processor and then you can see all compatible motherboards. Personally, I'd go for something by ASUS, GIGABYTE or MSI, just take care of having enough S-ATA slots etc.
You mentioned 'good' hard drive. Imho, no 2TB hard drive will be good for gaming (unless it's some sort of multi-RAID.
If you want to speed up your system you could/should think of buying a SSD.