[mr_alberta]

I think a 75 is a nice size to start with. Since, I assume, you are relatively new to the hobby, a larger tank will be a little more forgiving to rookie mistakes we all make when we first start out (i.e. like not topping off the water or changing the water as often as we should).

In my opinion, I would get a reef ready tank (that is a tank with an overflow built in and a hole or two drilled in for bulkheads). That way, you don't have to muss around with drilling the holes yourself (or getting someone to do it) and building an overflow box, etc.

I personally don't like canister filters on my tank for a few reasons. For one you have to have more stuff dangling from the back of your tank, and secondly, I find them a pain to clean.

I think that a protein skimmer is an invaluable piece of equipment. If you ultimately decide to turn your tank into a reef, I think it would be wise to invest in a good quality skimmer (or make one or get one custom made).

As for liverock/sand, there are a lot of people on this forum who are moving/selling off their system, so you should be able to score some very good deals on rock and sand. Just take a quick peek at the classifieds section (people like mnoll, teevee, Trevor Robertson are some that come to mind off the top of my head).

Just remember to take it slow, ask a bunch of questions, and have fun in the hobby. We're all here to help each other out.