That motherboard will NOT need a BIOS update to use the newer Haswell Refresh CPU (ie, the 4590). You should definitely go with the 4590 if they both are the same price. Other than searching on Google, a quick way to check if parts are compatible is by using the website pcpartpicker.com
I have input the i5 4590 and the motherboard you would like to select in the website and it gives no "warnings" or "compatibility issues" so that is another very reliable method of checking.
Here is the link:
http://pcpartpicker.com/p/b9wDkL
As you can see, no compatibility issues or warnings, so you'll be good to go with these two.
thx for the heads up, but I'm not too worried. I don't have the money to buy a more expensive mobo. And for my audio recording I use a focusrite scarlett 2i4. Its a USB 'soundcard'.