a bigger sump would allow more room for equipment [heater, skimmer, pump etc]
you could look at getting a second-hand eheim return pump from a member here instead of the one you were looking at. prob. better quality.
the more you spend on the skimmer, the better. if you get a good one it will allow you to keep more livestock in the tank.
the clownfish are pretty easy to keep, however you may want to hold off on the anemone for a while. apparently they are a wee bit difficult to loook after.
if you just want soft corals, then flouro lighting should be fine. metal halide lighting is what most people with reef tanks have, but these are quite expensive. the advantage with them is that they throw out enough light to keep hard corals etc.
i think the live rock to litres of water ratio is about 1kg rock to 8litres of water.
the more flow in the tank, the better. ideally you want no dead spots for gunk to collect and decay in. i have a few small powerheads in the tank as well as a couple of bigger ones.
im sure that heaps of people will be able to help you here..