Gravel advice sought.

Hello people!

I'm just starting to set up my first big planted tank (60 gallon acrylic),
and I need some help with gravel.

Most likely I'll be getting my gravel in bulk from a local landscaping
outfit (since getting enough gravel from a pet shop to make a five inch bed
would cost me a mint!), and basically am wondering what I should look for,
and what to avoid.  

My big considerations are that I need a rounded gravel (to help minimize
scratches, and for the sake of my bottom-feeding fish), which won't
drastically change my water's pH (I keep it at 7.4).  Would run-of-the-mill
rocks and pebbles be fine?  What about sand?  Any other recommendations?

FWIW, I'm not using a UGF, and I'm not going to go nuts with the whole
substrate thing (not yet, anyway)...the best I'll do is C02 injection and
ball-form laterite.

Thanks for any help!

benson at sd_znet.com