As other pointed out you are on the right path. Be sure to ride various bikes. What fits one person nicely may not fit an other. I have an '08 Garry Fisher Nirvanna as my year round commuter. Some things I found that I realy appreciate is that the cables all run on the top tube. Riding here in the frozen North all winter long, this design has helped the cables stay a lot cleaner. This is clearly a carry-over from the off-road bike experience that Garry Fisher has. If I were to get a replacement bike today I'd definitely look for disk brakes.
You would difinitely want to get some fenders. Rain can come quickly and frequently depending on the season when I've visted FL.
A simple but sturdy rack is easily found. You will have to figure out what kind of bags you want to use. I started with a cheapy set of Axiom Appalachia bags. I paid under $30 for the bags and they are completing their 3rd full year of commuting. I spray them liberally with fabric water blocking about once a year. The bags are not 100% water proof, but remarkably close. I carry rain gear with me all the time and also take with me food, drink and clean clothing. There are loads of bags that are "nicer," but I have been shocked at how good these cheap bags have been.
When it comes to wheels you are right that more spokes is generally better. My 1st OEM (Bontrager Camino) started blowing spokes badly around 800 miles. I got a 2nd wheel under warrentee. The 2nd wheel started to get bad around 4000 miles. I had a new front wheel built by Peter White early on as I wanted a generator hub. That wheel has only 32 spokes, but that is plenty for a front wheel. That wheel after nearly 5000 miles of use is still spot on perfect and has never been adjusted since I got it. When the 2nd rear wheel started acting up I had Peter build me a 36 spoke rear wheel. About 1000 miles in, it is holding up perfectly.
You should be able to find a perfectly good commuter bike for around $600 to $800. That leaves some money for the extras. Don't forget about a good pump (Topeak Road Morph G is my personal favorite). Lights are a must for riding at night. Do some searches on older posts as there have been lots of discussions in this in the recent past. Some good moisture wicking clothing will be very helpful. I personally have bought the majortity of my shirts on sale at Dicks Sporting Goods for around $10. Sure cyling jerseys are nice, but I just can't justify spending $60 on a single shirt.
Happy riding!
André