I think it would be best to let the OP listen to the different horns we recommended, then decide on his own. Bear in mind that the only signal that’s actually in the 9050’s compatibility sheet is the Commander series. The other devices (like the low-frequency sounders or Vibratone 450E) are either too new or too obscure to warrant being added to the sheet. However, below are the sounds each of these signals make, so you can decide for yourself which tone you think best fits the building. None of these videos belong to me, but I am simply using them for reference.
Another thing, since the 9050 outputs FWR rather than filtered DC, on the off-chance you install Truealerts, be aware that FWR has been known to fry Truealert signals, so I would not recommend using them.
What Wheelock does is make a http://www.cooperindustries.com/content/public/en/safety/notification/products/life_safety_notification/audible_visual_appliances/strobes/wheelock_series_rsspstrobeplates.html retrofit strobe plate called the RSSP, in both red and white. What you could do is have Federal Vibratones on one signal circuit, coded to Temporal (Code 3) and have the RSSP plates on another signal circuit, with Wheelock sync, and the strobes should all sync up with each other. Of course, you’d probably have to use white RSSP plates so that the 450E doesn’t look silly sitting on it. It would provide FIRE lettering and strobe coverage, albeit in a rather strange-looking signal.
Again, this is my opinion, and since I’m not a tech or professional, it should be taken with a grain of salt.