You should be able to get a fairly good used steal frame set on ebay for around $300.

This Tomassini Columbus SLX set sold for about $350 shipped.

This Trek Reynolds 531 frameset sold for about $220 shipped.

This Colagno Columbus set went for $270 shipped (through you would want a powdercoat)

I would take any of these over a new Surly 4130 bike (you should be able to get a lugged 4130 with similar geometry for $50 or less) or a Soma cro-mo.

A Salsa LaRaza with TrueTemper OX on the other hand, might not be so bad and the Primero looks great.