I really don't want to give up speed.
That is going to be tough to do while riding a flat bar road bike. Most on the market that match that description are fitness bikes, with heavier components and frames. Much heavier. They are not built for speed.

I have a Giant FCR, which is the bike I started out on. It has flat bars. The bike is great for what it is intended for, just riding around. But it is not fast, and for anything over 5 miles I start having hand issues becuase there are not enough options for hand placement. Compared to my road bike, it feels like a beach cruiser though! it's got 35mm tires on it and rides like a Cadilac.

I would try a stem with a rise to it first. Millimeters make a difference! It doesn't have to be a huge change to address a pain issue.