You can have a "aggressive" race bike but it's not going to be comfortable on a long ride in comparison to a bike that puts your arms higher on the bars.
I chose the H2 fit on my Emonda, and even with the stem flipped and slammed, I'm still not automatically flat-back low on the bars (plus I purchased the bike in a traditional size - I didn't drop down a size, like lots of cyclists do). In fact, my 2008 Specialized Roubaix, with its epically ginormous head tube, has a stem that flips into negative territory (my Emond's stem doesn't), which can potentially put me lower on the Roubaix than I can get on my Emonda!
On the other hand, I'm slim, slimmer than Sagan and Cancellara and I can get low enough on my bars that my thighs just start to touch my stomach. So I can get very low on my Emond. But that's not a comfortable place to be on a long ride.
Anyway, the Emonda isn't a aero bike. It's certainly a comfortable bike for long rides - I'd have no qualms about taking it for a century spin. I think it nicely splits the difference between an endurance bike and a pure race bike, with the added benefit of serving as an awesome bike for taming the heights.
If you're current bike doesn't put you a lot lower than the Emonda would, then don't worry about it. If your bike does drop you a lot lower than an Emonda, and you truly ride in an aero position, then you'll go a little slower on the SL 6 - but you can work just as hard. Unless you're racing someone, you'd never notice a difference.
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