What a lovely house. Since you have wood, I would stay with wood. If you decide to go with something else, consider stone or simulated stone. My fear with trex is it might be slippery in winter. Also, please consider removing the poodle shrubs, it doesn't fit with the overall design of your house - unless Mickey House is in residence. I think topiary hedges are interesting to look at, just not up next to a house - because it has a gives it a commercial Disney appearance. I also love the turret portion of the porch.

I would stay with wood...might consider adding a small landing about midway down.

I say wood, it already compliments the front of your home and will continue to work cohesively!