Last time I checked the Teague stuff is cheaper than any Merc Blue motor. Most of the time you can get a Teague 800efi with XR drive for the same price as upgrading to a 525 or 600. Unless DCB is jacking up the Teague prices...
BTW Teague offers the same 1yr warranty as Merc.
Of your 2 choices, I'd definitely agree go 525s with the possibility of Whipples later on.
-Tom
You'll have a much better chance of using the teague warranty. If you can keep the blower belts on.