What rock should I use?

[Bartman]

Hi All,

For my 75G I was thinking of going with about 25 lbs of base rock and 50 lbs of live rock. What should I use for the base rock? J&L has Reef Rock for a little over $1/lb but it is dense and doesn't appear very porous. Big Al's has Tufa which is light and porous but they want $2.79/lb which is reasonably close to live rock prices. Is there, perhaps, another alternative.

I've seen some DIY rock which gives good shapes but is also fairly dense and solid.