Kriston-

Singapore math is very popular with gifted kids. This is the program used in the public schools in Singapore, and kids from Singapore tend to exceptionally well in international math competitions. It's very inexpensive but quite thorough. Take a look at www.singaporemath.com and see what you think. There are sample pages to be viewed, and you can print out a placement test to gauge the correct level to begin. Keep in mind that SM tends to be 6 months to a year ahead of most American programs, so a child doing Saxon grade 3 might only place into Singapore grade 2.

Don't bother with the Earlybird series. These are labeled for kindergarten, but they are VERY basic. Head right into the real Singapore series. You probably don't need a teacher manual for the primary gardes, but you should get both a workbook and a "textbook" for each level.

If Singapore doesn't seem a good fit, you can try Miquon, another popular program, or perhaps consider online math with EPGY or Aleks. But I think you get the most bang for your buck with Singapore.

I'd also recommend mathy prose for your verbal oriented son. See my articles here:
http://www.bellaonline.com/articles/art33626.asp

http://www.bellaonline.com/articles/art28465.asp

I hope you'll have a blast homeschooling your little guy!