1.) after you upgrade, you won't have to buy another power supply
2.) a good power supply is quiet, lasts longer, is more stable for OCing, and decreases your chance of anything frying
Most stock PSU's that come with cases are cheap made, and pretty much useless. Unless your case comes from someone who makes decent PSU's (Antec, ThermalTake, etc), it will most likely have a puny or crappy PSU.
Make sure there is enough amperage on the RAILS because if the amps are to low then it wont matter how many watts you have unless its like 600+ lol but there are no stock psu's with 600+ watts... Anyways my raidmax with 13 amps on the 12V+ rail is just enough... Even though it gets hard running 2 cd drives with 2 HDD's on a 64bit board...
Make sure there is enough amperage on the RAILS because if the amps are to low then it wont matter how many watts you have unless its like 600+ lol but there are no stock psu's with 600+ watts... Anyways my raidmax with 13 amps on the 12V+ rail is just enough... Even though it gets hard running 2 cd drives with 2 HDD's on a 64bit board...