You can always try it first without forced air cooling to see if you have a heat problem.
Another option for cooling is to duct the air from and then back into the basement. You could have one or more fans on one end of the bottom shelf that pull air from the basement, one or more fans on the other side of the bottom shelf that pull air from the cabinet into the basement, and fans internal to the cabinet to circulate the air past your components.
This must be done properly.
That the OP is thinking of cooling equipment is a very good thing. After doing a couple of years at a retail/custom install company my top issue was seeing installations almost identical to this where the gear wasn't cooled at all, then broke down within a month or two of ownership.
The reason I say this must be done properly is that air tends to track along a pathway that is easiest to follow.
If you vent cool air into the bottom, then vent it out the bottom, then the hot air at the top will never be moved out. Air does NOT want to be pulled down, instead the air at the bottom will actually circulate in, then right back out again and the hot air at the top will actually be trapped at the top. You basically create a mini cold front at the bottom of the cabinet preventing the warm air from escaping.
What you always want to follow as a rule is to provide a single point of entry for cool air at the bottom of an otherwise sealed cabinet and provide a point of exit as high as possible in the equipment rack. The fans should always go on the exit side of the rack to pull air through the rack. The entry and exit points should be of the same size to allow for even airflow through the rack.
In an ideal situation, you might have the top of the rack not actually touch the top surface directly. That, of course, takes some serious pre-planning to accomplish or a serious modification.
But, if you provide a duct vent and a decent fan to pull hot air from the top of the rack, and provide a simple vented opening to the bottom of the rack, you should be able to get adequate airflow moving upwards through the rack and venting into the basement.
Keep in mind, that if you ever finish the basement, this will still need to be maintained.
NOTE: Venting into a space which does not have airflow is NOT venting! The air will not actually have anywhere to go and will just create a circulation of warm air or back up all the warm air completely.