How much solar power is needed is a balancing act with a number of considerations. Conservation is a big part part of the equation i.e. use of LEDs. How much you need/want is dependent on what you plan on powering, anything using resistant heat is a power sucker, we do not even use an electric coffee maker, the french press makes great coffee. but we do run the XM sat radio, TV and Waeco refrigerator and all LED lights.
How much is dependent on where you camp and how much direct sun you will get, if it is in the trees...
We have a 185W high voltage panel which feeds a Morningstar MPPT controller and it will generate usable current in low light situations I also have a Unisolar 140W flexible panel I can unroll out in the sun, which I have yet to use as the 185W has met our needs.
The Harbor Freight panels are low efficiency and the cost per watt too high. I am seeing 100W panels for $150 on ebay with shipping with out doing much of a search.
Home work, one of the best if a bit opinionated, sources of information is Handy Bob http://handybobsolar.wordpress.com/