Will a MSI GeForce GTX 1070 work in my pre-built ASUS M32AD Desktop?

Solution
PSU wont be sufficient for a GTX 1070 so you will need a better one.
No idea what you have for CPU, i5 will mildly bottleneck, i7 will be fine, i3 and lower will be hitting a brick wall.

Also always a probability of cooling issues in OEM case. They dont often have slots for large front and rear fans (often running off of a single 80-92mm fan).
PSU wont be sufficient for a GTX 1070 so you will need a better one.
No idea what you have for CPU, i5 will mildly bottleneck, i7 will be fine, i3 and lower will be hitting a brick wall.

Also always a probability of cooling issues in OEM case. They dont often have slots for large front and rear fans (often running off of a single 80-92mm fan).
 
Solution