I like Afterstep personally. But it isn't very aquaish. There is another one, supposedly VERY aqua like. Called Orbivs or something... someone post please!
Try Oroborus, although it doesn't by default come with an Aqua scheme. If you get OroborOS X, that program will allow you to run XDarwin applications alongside the rest of your applications, with an Aqua scheme to boot.
OroborosX is an awesome integration into aqua. You really can't tell the difference until you see your cursor change. If aqua like is what you want, this is clearly the way to go.