The roof radiant barriar is the best return on investment you will make. Passive ventilation with air entering at eave and leaving at higest point practical is also cost effective. Vent fans certainly cut down on transer of heat to conditioned air but probibly don't save much operating cost. Extra insulation of air handler and ductwork helps quite a bit.

Check with local experts to see if sealing the attic space and insulating the roof deck is advisable in your area.

OK, thanks for information. I hear you that 1) radiant barrier and 2) passive ventilation will help and are cost effective.

We have an interesting situation with the passive ventilation issue. The attic space created by the knee wall runs along the full width of the front of the house. Continuous soffit venting is an option for 50-60% of the width. The remainder is taken up by a front porch roof that comes off the front of the house perpendicularly. So we can not have soffit venting in that portion. The gable does have a sizable gable vent, but I doubt that will provide the same amount passive venting as soffit vents. As of right now, there are no plans to create cross ventilation in the attic space by putting gable vents on either side. Should we plan to do that? Considering these factors, is an attic fan (or some more complex power venting) more or less advisable?

Thank you again for your help and advice!

Power vents certainly work but only by consuming electric power that may as well be consumed by hvac. Then you have inital investment for the fans,be they solar or 120 volt. 50% of soffit area is more than ample,esp if it is bisected near the center by the porch. Soffit vents arn't near as effective in absence of gable,ridge or other vents for air entering soffit to exit at high points. I sense you aren't prepared to diy so maybe you shouldn't attempt engineering it via internet before hireing someone to carry it out. Let your carpenter and/or ventilation contractor decide where,how many and size vents.

We will have ridge venting. Baffles will be installed under roof deck with batt insulation between 2x10 rafters. There is a tiny unfinished attic space at the very top. To reach the soffit vents, the baffles will need to enter the unfinished attic space behind a knee wall. Does that introduce any concerns?

Also, the porch is actually positioned all the way to one side, so the porch side can not have any soffit venting. As I mentioned the porch does have a sizable gable vent. Would installing gable vents on either side of the attic have any tangible benefit?

All of this is being built as we speak and I am mostly seeking advice so I can make sure the contractors know what they are doing and do the best job possible within budget.

We will have ridge venting. Baffles will be installed under roof deck with batt insulation between 2x10 rafters. There is a tiny unfinished attic space at the very top. To reach the soffit vents, the baffles will need to enter the unfinished attic space behind a knee wall. Does that introduce any concerns?

Also, the porch is actually positioned all the way to one side, so the porch side can not have any soffit venting. As I mentioned the porch does have a sizable gable vent. Would installing gable vents on either side of the attic have any tangible benefit?

All of this is being built as we speak and I am mostly seeking advice so I can make sure the contractors know what they are doing and do the best job possible within budget.

I sincerly hope you take this exactly as I state it because there is no hidden message.
There are many ways to derail relations between the consumer and contractors. Close to the top of the list is trying to supervise an ongoing job by talking to the workmen about information you got from your neighbor,brother in law,another company,ect ect ect and of course a fella on the internet whom you never knew existed until he gave you some advise.
Trust me ,contractors despise that kind of help.

From personal experience, I will never assume that a contractor uses up to date or best practices.

Some contractors are good for a particular job and some are not. For example, 2 of the 4 insulation sub-contractors I was considering had no intention of sealing the spaces under the knee wall created by the floor/ceiling joists. I am not an expert but a multitude of sources including Energy Star recommend this step.

Any thoughts on double baffles, vents on the side gables, etc?