Well, he's decided to look into some other armies after reading on the interwebs. Necrons have caught his eye, as have the 'Nids. DE are also on the block. I've suggested that he borrow armies from some local players who already own them and have a couple of small games to get the feel before buying anything, and that if possible he should look at what considers Chaos Space Marines allies so that he can still use his existing models.