what n/a 93 octane big block, let alone small block is making 650hp on the street or around 525rwhp? It is easy to make well over 600rwhp in a turbo application with very low boost levels. We are talking on the lines of ray barton hemi power territory with a simple, pump gas 400+s480 turbo combo @10-12psi, low compression, max power well below 6,000 rpm, and 2.76-3.23 gearing.
To answer the op's question, i believe the turbo is by far the best route and most cost effective. An s480 (1.32ar) is $1,000 new. Add in a used $500 csu blow through carb, etc. And you'll be at around $3,000 when its all finished with the nickel and dime.
A blower application from 'the blower shop' will more than likely cost you double, if not triple this amount to make less efficient power and less power overall, all while giving poor fuel economy (two big blower carbs) and a torque curve that is terrible for the street, as it just will blow tires away.
A supercharger, such as a paxton or procharger are great alternatives. Still, once again, not nearly as efficient as a turbo application but very easy to install in comparison.
