actually, if you add that much live rock, you're going to have a major problem and recycle the tank.
Instead, what you might do (if you want to head towards a reef tank) is add about 30-40 pounds of 'dead rock'
http://reefcleaners.org/index.php?p...ategory_id=15&option=com_virtuemart&Itemid=34
Wait for that rock to get a good build up of bacteria (say a week or two), then add about 10 pounds of
already cured, high quality live rock.
This will take a little longer to build up coraline and critters and such, but it is (IMHO) a much safer way to move toward including live rock in your tank (regardless of if you want fish only or reef).
So, yes, put the base/dead rock in, arrange to suit. I suggest that once you get it arranged how you want it, use a good quality, aquarium safe epoxy to fuse all the pieces together and then lower the whole shebang into the tank at once. I basically made a template of the floor plan of my tank (it's an odd shape) on a piece of cardboard and arranged the rock how I wanted it, then epoxyed the heck out of it. I used the pieces and sand to stick into the epoxy before it hardened to mask the material.
If you want anything reef, I also suggest you upgrade the light... at least 96W PCs, preferably more.
Another thing is you might want to add some filtration in the form of a canister or HIB filter. I've got a sponge and a HOB on mine. The HOB is mainly for filtering big chunks of stuff and an easy way to get phosphate remover, carbon, etc into the system.
There's lots of people here who can help out. Read lots before going reef, but it can be pretty awesome. Luck