We went from Singapore 6 almost directly to NEM.... Almost, because we spent a summer playing with a free Kinetic Books algebra download, which was cute but not really one I'd recommend if it weren't free. Also we had dabbled in Gelfand's Algebra, which I would love to have used straight through only it's challenging to the point of being almost harsh... and DS was only 7-almost-8. So we ended up with NEM.
The way we did it was to do the first two books, Algebra topics only, in one year. Then we took a year "off" (last year) to do Statistics... And this year we're back with NEM for Geometry. At this point it's almost too light, but we're adding in a separate book of Mathematical Logic which beefs it up a bit, and we're doing just about a whole curriculum's worth of problem solving, pieced together from AoPS books, Jacobs' Mathematics A Human Endeavor, online sources, MathCounts and Math Olympiad materials, old AMC tests, and two groups of kids... which comes to what, triple math? LOL
We're oddities in this, not just for the acceleration -- also for really excessive interest... But NEM isn't as scary as people make it out to be. The first four chapters are trying to kill you with a comprehensive review of arithmetic (LOL), but after that I think it's very reasonable.
