I would recommend going for at least an R9 380. The R7 370 is a rebrand of the R7 265, which is a rebrand of the 7850. Besides the OEM-cards, the R7 370 is the only card in the 300-series line-up which is still based on GCN 1.0 technology. This means it doesn't have GCN 1.1+ improvements, and lacks TrueAudio (not that the latter is much of a breaking point...).
Second of all, either forget about Dual Graphics (formerly: Hybrid Crossfire), or wait what MS's claims concerning DX12 and mixing multiple types of videocards for Multi-GPU holds of value.