When DS was six he did EPGY grade 3/4 math. It is a very thorough program, but the interface is old and not very snazzy. It also has a lot of bugs. I'm glad that we tried it, but I decided not to spend the big bucks for it again at the elementary level. You might instead consider Aleks Math or Larson Math if you want an online program (not sure if Larson is still around) these two programs are considerably less expensive.
DS did eventually go back to EPGY for algebra. He also did Singapore math and a year of Larson. I really like Singapore and feel it has a lot to offer for a fantastic price. One other plug for a new favorite: We discovered Life Of Fred math just a few months ago. (They don't have an affiliate program, BTW, so I don 't get any compensation for recommending them!) My dd and ds both found it fun and amusing, though dd only read the story in the Trig book and did not attempt any of the problems. I reviewed them here:
http://www.bellaonline.com/articles/art25135.asphth-
