Soil Sampling Equipment Recommendation:

JMC Environmentalist's Sub-Soil Probe Plus ($2650-$5900)
Even though it requires plastic liners, this probe still deserves consideration. It features a sliding drop-hammer and a foot-operated jack. Great system for all soils now and more capabilities later.

JMC T-Handle, Mallet, and JMC Large Diameter Sampling Tube ($260-$630)
Inexpensive method for sampling hard soils.