Sorry I can't offer any suggestions as what you propose isn't really feasible at the moment, or will it ever be for commercial fonts. The best you can hope for is list the font in your css first, then let it degrade to Verdana or something, so at least if someone does have the font they get what you want.
sifr is a lazy solution to a problem better solved using image replacement. The flash player is very CPU intensive, and if you have lots of sifr embedded, people won't be able to scroll your page smoothly. Limit use of this only to h1 titles if you really can't be bothered to make the images (or a script to generate the images).