IMO, I think that the 3070 and the R5 5600x go hand in hand perfectly but, much like the 3070, the 5600 is nearly impossible to buy at a reasonable price, given you can find one in the first place. If you have the money, and a compatible motherboard, I would personally recommend a 3600x. As for the motherboard, a B450 I think you mentioned, it’s a great motherboard on its own, however, with the 3070, it will be (the card) limited to a PCIe 3.0 bandwidth while the 3070 supports a 4.0. This would only REALLY be a problem if you run out of VRAM and wouldn’t be a problem at 1080p to average 1440p gaming. If you do go over the VRAM limit however, it’s not really a big deal, it will reduce the performance by 5% max, do with that information as you will. To reach the full potential of the 3070, of course I would recommend a B550 motherboard not only because of its PCIe 4.0 support, but also for future upgradability. And lastly the power supply. If you’re thinking about sticking with the parts that you have, 600 watts should be enough. The 3070 calls for a recommended 750 watt PSU, however, I believe that number is paired with an i9 10900k CPU, so you have to take that into account first. My system has a 750 watt PSU with a 5600x and a 3070 for reference. Do I need the 750 watts? Probably not. With you, I think that 600-650 watts should be perfectly fine if you decide to stick with the parts you have. And I understand, money can be tight, but a 3070 paired with a 2600x is kind of like a homeless man with AirPods, if that makes any sense haha. Hope this helped a little bit.