Hey coffeelover,
We're pretty similar in some respects. BAV (mines now a ticking carbon bi-leaflet aortic valve mind you), allergies, sinus headaches, occasional migraines and a love of coffee. I have never considered a possibility of connection between sinus pressure and the BAV or the stenosis or insufficiency, and don't think it's too likely given that it wasn't improved by the replacement of the valve. I know too, that sometime those allergies can be to inside things, like dusts, molds, mildews or pets, perfumes and houseplants. The migraine on the other hand, is likely associated with (not caused by) the valve issue. It's not well researched or documented but there is ample anecdotal evidence that we BAV folk often have other developmental issues with our circulatory system, including a weak aorta, and a susceptibility to migraines, whether the headache type, or the visual, olfactory or sensory type.
That's not really the answer to your question though so: No, I haven't had sinus pressure that worsened as the valve stenosis progressed. At least I don't recall that happening.
Paul
PS I presume you're aware that coffee can stimulate those migraines? Most migraine sufferers know this but I thought I should mention just in case.