If you KNOW you're looking at 6 years, just put it in a CD for 5 years and a high-yield savings for the last year. It will give you flexibility if you find the house slightly early. That's if you need the money to be "safe" psychologically. I would just leave it in, but that's a risk you have to decide if you're willing to take. I'd rather have the (probably) more money. And hey, if it dropped substantially, probably so did the housing market.
You could alternatively use the stuff you mentioned, or something like Discover Online CDs at shorter terms around 1.35%, if you wanted it more liquid, for a rate better than the high-yield but lower than a 2% CD (where's that?). Or, municipal bonds, tax-free. That's all I can think of.
Edit: nevermind, Capital One 360 2.00% for 5 years seems like the "not the market" winner.