Just to clarify, this is a 2.5 gallon batch. Sorry if it looked weird.
Regardless, I am loving the opinions here. The reason I was thinking some D-180 or D-90 would be good is because I was thinking the dark fruits, baker's chocolate, light coffee notes would go well in a porter. However, I was a little worried that it might dry out a beer like this where I was thinking of adding oats, or that it just sounded out of place in a porter.
The thing to take away from this thread is there are no hard and fast rules. IME dark candi syrup always reminds me of the raisin like character you get in Dubbels. Same with special B. Using it doesn't make it wrong, and if you sub it out for malt it will ferment drier - and the roast character of a porter may actually mask that character somewhat so I may be completely wrong (but not ridiculous ). My personal preference for a Porter is stated above, all malt. Doesn't mean it can't be brewed another way but if my opinion is asked on a public forum I can only give it, not someone else's.