I'm a pretty casual gamer so I'm not looking for anything too intense. I can deal with what I got, just looking to see what would be the wisest investment. I thought SC might be out of my reach, but I'm fine with playing WOW.
So I'm guessing I should first improve the power supply? How much could I get a good 450w for my motherboard anyway?
Go with 2.0. And its because they over judge what you need for a PSU, this is to cover all their bases. Maybe you have 10 hard drives, or maybe you like to overclock, or maybe your PSU sucks. They don't want to say you can get a 300w PSU and then it not be enough.
But that card only draws power from the PCI-e slot, it litterally can't consume more then 75w of power.
Well I personally don't got by what the manufacturers state but by what I know of the card to actually consume then apply that to what I have learned over the years about power supplies.
At full load a 5770 can use 84w at stock and top out around the same as a 8800/9800gt through overclocking around 105w. The 5670 and gt240 are more or less the same under load. The gts 450 at stock and under load is 105w while the max is a matter of debate. Those are some very basic values for power consumption and in actual gaming use can vary greatly.
That psu is a limiting factor but you can go ahead and roll the dice. It may be able to take the load like a higher rated unit and last for years but no unit is the same. Heat at that point is something you may want to keep an eye on and be sure to keep the clean. Dust and heat are the enemy of power supplies.