What is your resolution?
I have a five year old computer and use a 32" flat screen TV as a monitor.
The clarity and size of the unit, while playing the game is fine.
I remember playing on a 21" monitor and it was O.K. too!
If you play in 3-D I suggest using unit bases. Turning on the thermometers as Jason mentioned. Also, I play with reachable hexes, that highlights where a unit can move (though I switch back and forth between visible hexes and reachable hexes). Range, which displays how many hexes a unit can reach out and touch the enemy, with hard and soft attacks.
I hope that helps.
I use 2-D when I play larger scenarios. And, mostly for movement.
I like to fight on the 3-D level regardless of scenario size.
“The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane.”
― Marcus Aurelius, Meditations