Hello dudevato,
First dump the computer if it's a desk top, get a laptop, will save you money.
Many laptops can run off 12v directly or at least with a cheap booster (28$).
Desktop will draw 120 to 200w, all depends on what system you have.
Then the monitor can draw another 70 to 150w, look on the label. Like the other guy said use LCD.
Solar power cost $6/watt, so to make it with a desk top 150s + 100w = 250w * $6/w = $1500
My laptop 1.6ghz draws 30watts, for the computer and display. Solar cost is $180.
Take the difference (1500 - 180 = $1320) and buy a nice laptop!!!
Then get rid of the stereo. Car stereos used to be a good choice until they started producing the 500w ones. Maybe a nice boom box, with efficient speakers a lot of power is NOT needed to make a lot of noise.
With solar, you can replace your "loads" with newer lower power units and save money in the long run. Each watt saved, saves >$6 in cost to produce it.
I have over simplified some of the issues. Do not buy anything until you understand what all your options are. Later you will be wishing you had.
Have fun,
Scott.