The short answer is "it depends".
There are banks out there doing second mortgages specific to your situation (with caveats, of course). There are also Mortgage Insurance carriers allowing for up to 95% financing these days, so "it depends" on how much over $417K you want to go (80-10-10s do not necessarily need to be exactly that). Howard is correct in that "it depends" on a number of factors, and a FICO > 700 is one of them, along with income and assets (reserves, etc.).
Conventional is the only non-jumbo loan which goes as high as $417K here in Maricopa County, so that type will be your only choice.
Give me a call on Monday and we can go over your total situation to determine which is best for you.