I use the same power supply as you. 5-7 min heatup time For 120 bed and 250 hot end. Hot end is lightning quick bed is slow as it should be. I got it off amazon ill look it up wheb i get home and post a link.
12v 30a Dc Universal Regulated Switching Power Supply 360w for CCTV, Radio, Computer Project https://www.amazon.com/dp/B00D7CWSCG..._k.BUub15SDVGZ