Ging, I've found that I like the look of my tank with slightly less then 1.5 pounds per gallon tank capacity. I have 250 pounds in my 180.
It really depends on what look you are trying to achieve. In your case, I'd recommend that you start with about 150 pounds and then go from there. Until you know what look you want to achieve, it's a lot easier working with a little less LR than with too much, because otherwise you run out of places to put pieces of LR that you haven't stacked yet. I'm pretty picky about my aquascape, though, and it took me about 12 hours over the course of two days to get my LR stacked in the new tank, and now I'm thinking of rearranging it again.
As far as type, get what looks good to you. Look for rock with good coralline coverage to seed your tank. I am partial to Fiji rock, as that's what I use. Like you, I started with LR from the LFS (it was Fiji) and didn't realize how crappy it was until I got some Fiji by mail-order. I had all LFS rock in my 115 gallon system and then got an additional 100 pounds from Paragon when I moved into the new system. I was really surprised by how much better the mail order rock looked than the rock I got from the LFS. So I wouldn't recommend filling your tank with rock from the LFS unless the rock really looks impressive.
I don't have any experience with the aquacultured rock but people seem to like it. It is denser than natural LR, however, so you'd need more pounds of aquacultured rock than natural rock to get the same effect. I like the natural rock because it's really light and porous and is not too heavy when you're working with it and stacking it.
I'd actually be interested to hear from people who have experience with both Fiji rock and aquacultured rock, to see what their opinions are. Also, if you start with aquacultured rock you'd probably want to stick with it because it will look a little different than the natural rock, and mixing them might make things look funny. (Anyone out there done this?)
Hope this helps. Good luck with the new system.