What is the meaning of "Gever Chacham ba'Oz"?
Rashi: A Chacham is always with strength.
R. Yonah: After mentioning that wealth is found with Chachmah, it mentions that [also] Gevurah is found with it; Chachmah does not lack anything. A Chacham is a leader and officer over people of Oz (Giborim); he leads them out and returns them. Via his counsel, they overpower and succeed - "Ir Giborim Alah Chacham" (21:22). "Ba'Oz" means b'Anshei Oz; ['Ish' is omitted], like "va'Ani Tefilah" (Tehilim 109:4) - I am an Ish Tefilah.
R. Yonah (6, according to Mashal): This is like "u'Moshel b'Rucho mi'Loched Ir" (16:32).
Malbim (according to Melitzah): A Chacham is one who received the laws of Chachmah and conducts according to them, he has strength to overpower enemies of the Nefesh - desires and Yetzarim of the heart. He subdues them with the Chachmah that he received.
Why is an "Ish Da'as Me'ametz Ko'ach"?
R. Yonah: A Chacham is a leader and officer over people of Oz; an Ish Da'as is greater. He invigorates people's strength with his Da'as, even if they are not people of strength. An Ish Da'as encompasses people's thinking. Most wise people, each one has one way of thinking; an Ish Da'as sees all facets that many Maskilim see, and thinks all that "Shiv'ah Meshivei Ta'am" (26:16) think. Among all these, he chooses the proper way. His counsel is in place of many advisors. His counsel invigorates the strength of those who stumble. He brings salvation from affliction, for he thinks of ways of salvation, until he finds the one that will succeed, like the coming verse says "u'Seshu'ah b'Rov Yo'etz."
R. Yonah (6, according to Mashal): He invigorates others. He understands their nature and Yetzer and teaches to them the way of Teshuvah, and to be wise against their Yetzer. An Ish Da'as gauges mindsets, the opposite of "Rasha Lo Yavin Da'as" (29:7).
Malbim: This is a higher level than a Chacham, who subdues desires of the heart. Imutz is to always remain in his strength, without change. Chachmah alone does not suffice for this, for the Yetzer ha'Ra constantly fights with the heart, since the laws of Chachmah are not understood like sensed matters. Sometimes the Yetzer ha'Ra overpowers, and blinds the heart's eyes. An Ish Da'as knows the laws of Chachmah as clearly as something proven or sensed. He always invigorates; enemies of the Nefesh never overpower.