These are fantastic suggestions - thanks everyone. Let me digest these a bit and I'll let you know which one we wind up going with. I'll probably throw a few suggestions out there and let the group pick...
Pardon me for the self-promotion, but I'd honestly say that you might want to consider HackMaster Basic.
The system strongly supports thinking tactically as an effective way to succeed in melee. Working with your group and planning out effective combinations of shields and reach weapons (such a character with a spear behind a character with a shield, just to give a common example), is a huge advantage over rushing into a disorganized scrum.