Your height isn't the driver for frame size...it is your inseam measurement. You inseam is likely in the 34-36 inch range and yes that is likely to drive you to an ideal frame that is a bit bigger that a 64cm. Probably a 66cm or so. Can be hard to find off the self. At 206lbs, you are not really heavy for your height. Given your $400 limit, I think you are really limited to a lucky find of a used, custom built complete bike (they exist and do come up for sale here and there...) or living with a 64cm equipped with upright bars... Best place to find one of those off the shelf is to look for a hybrid bike, such as an XL size hybrid on
www.bikesdirect.com Should be several there in the $400 range.