There's still some doubt about the exact PSU, either 300 or 350W. In either situation, the PSU is likely to lack the PCIe connector you need to power that GPU. In addition, with a TDP of around 120W the R9 370 is close to the limit of what a 300W PSU can handle. The most powerful GPU without a requirement for PCI-e power is the NVidia 750ti.