No matter what my budget is, I always try to spend good money on my PSU. I've had a whole system become useless because of one bad PSU. My recommendation is save some money and buy a nice semi-modular one.
Get a used 290x for 300.
Edit: Nvm, just realized that gtx 970 runs as well as a 290x. In that case, I agree with everyone and say you should get a new gtx 970 or buy another 270x for CF if you're on a budget.
AMD cards tend to run hotter than their nvidia counterpart. I have a r9 270 that's heavily overclocked and it hits the same temps as you under full load. I've even had cards than ran at 90 degrees just fine.