The problem with a 300 Watt power supply is just that, it's 300 Watts. That was okay now but what about next year? An Antec TruePower 430 can provide a max of 240W of +12V alone, leaving 170W of +5V and +3.3V until you reach the 410W max output. A 300W Sparkle can provide a max of 180W of +12V but, if you use it all, it only leaves 100W of +5V and +3.3V until you hit the max output for the unit. At the same 180W of +12V, the TruePower would have 230W of +3.3V and +5V combined. It's really not a fair to compare to the two to each other. The Sparkle may be good but it's not a 400W power supply. A 400W Sparkle will cost $69 @ Newegg, that's more than the Antec for less features. No dual fans, no individual output circuitry. There are a lot of good 300W units out there, but they are all still 300W units. That's what will be the issue for you sooner or later.
300W Sparkle FSP300-60BT (12V):
+3.3V and +5V total output not to exceed 180W.
+3.3V, +5V and +12V total output not to exceed 280W.
Still looks like a 300W power supply to me.