You have great taste so it will look fantastic when you get done. Agree w above, no need to taper.

Thanks for your responses. I do think it's a totally different area, but I want it to look like a natural addition...like it was always there from the start. You can see both the front and back porch (one post of it) only from the side of the house if you're walking or driving up to it.

If you are concerned now is the time to make the change. I think it's going to bug you if you don't, lol. Like I said, you have great taste so go with your gut!

I agree with duplicating the tapered post, it will appear like a cohesive addition

Definitely tapered! I'm sure you can find a different type of shade, maybe like outdoor drapery.

The posts we were going to add are straight but much thicker, with wood trimmed out at the bottom (not stone). If we do tapered, it will be the same, trimmed out and then the base wider, in wood.

The front of the house usually looks different from the sides and back of the house. This can be seen when houses have brick or stone on the front but siding on the sides and back. Many people have shutters on the front only. My own house has a different look on the sides and the back. It was built in 1959 but I think the custom of putting all the razz ma tazz on the front has been around forever. I see no reason that you should conform to the look of the front. I would do what is the easiest and cheapest.

Two different areas, I don't think it is necessary myself

It's not necessary and trying to match the posts will look forced. It's like trying to match the front door and back door. They are two different areas.

Thank you for all your input. It makes a lot of sense. I would rather do straight posts, just wanted to make sure they wouldn't look too out of place. Now...another question: we have gable brackets on the front of the house, and a beam detail on the inside porch ceiling on the back that is different. For the outside gable on the back, would you match the gables on the rest of the house or would you match the bracket detail inside the back porch (which I like better)? I'll attach pictures. (The collar tie in the middle of the back porch is going to have the same detail, it's just not done yet).

On exterior of new I would do the same detail as front. Interior of the porch keep with what your doing in there as well. I think that detail on the outside will give you that continuity.

No the bracket details don't have to match. Forcing strict front to back symmetry on your house is neither necessary nor desired.