Edelbrock Heads Sound Like They're Terrible

As Rob said - never run anything out of the box. RPMs have issues - Indy has the same or worse, Stealth, same deal... I haven't had as bad an issue with core shift but guides, seats, installed heights (which is your rocker geometry), wrong/missing parts, cheap seals, and debris left in them are all what I've found problems with and they all have it. In terms of dollars - you need to be honest with yourself and the machinist. A good set of iron heads (not ported, but cleaned, magged, new guides, exh seats, cut spring seats, a 5 angle valve job, milling of head gasket and intake surfaces, OS valves, shims, seals, retainers, & locks - all costs and yields an open chamber head that's fairly heavy, and fairly limited in terms of performance unless you pay to port them, and iron porting can be more $$. The decision is not just cost. You get a more modern chamber to build with, a lighter part, and with no porting a gain in airflow going with the RPMs (or others). For a few hundred less you can get most of that with the RHS/Indy iron Magnums but they are heavier than the factory iron. In my experience the iron runs around $1400/set to get ready to install, the RHS about $2200 (plus rocker setup), RPMs about $2500 with the right head gaskets. None of those would be ported but all would gain a little over advertised flow rates with the valve job.

As far as intakes go - again - they all have issues. The Crosswind/RPM debate is constant. I know what my experience is, and I won't run a Crosswind.

As far as the steel/vs sand casting - The voids in any cast product have to be filled with something before the aluminum goes in. Sometimes is sand, sometimes it's foam, probably some other stuff too - at least going by the surface features "as cast" of the stuff I've seen. Pro Products uses sand judging by the castings I've handled.