The TP 650 has more than enough power for any single graphics card, it can also handle most of the dual GPU cards like the GTX 590.
When dealing with power requirements its the combined rating of the 12 V rails that matters since the card wont be pulling 38 A, it will be pulling 20 A at most, some of which is coming from the motherboard so its already spread among multiple rails, the 38 A rating is for the whole system since your average high end CPU needs about 10-12 A from the 12 V rail, and the rest of the system components puts your total load around 38 A from the 12 V rail under full power. For more on why the multiple rails dont matter http://www.tomshardware.com/forum/306437-28-single-rail...
, you should be fine. as each pci-e connector uses a different rail.
unless your going for mid 4Ghz overclocks on your cpu and plan on overclocking your gpu or if you have 10 case fans and 8 hard drives you should consider getting a better power supply. but a normal 1-2 HD and 3-5 fan system should run fine.
your current power supply will be running at 70-90% max load. you would need a power meter to be more specific than that.