I think the biggest factor is the limited availability. If I were in your shoes, and Byers/Hatfield happens to get one that meets your criteria, I'd take the small financial hit for simplicity's sake and get the new BRZ as soon as possible. Who knows how long it'd be until you see one again. Factor in that every day you drive your spec.B it's losing value, I'd say it's not worth the headache. If, and only if, you could get it paid off completely, would I say sell it privately first.
Just my two cents.