Active solar thermal for domestic hot water is something of an expensive Rube Goldberg contraption, susceptible to failure. In an Orlando FL location you'd be better off spending the money on a heat pump water heater (which gets half or more of it's heat from the room air, thereby lowering the air conditioning load) and grid-tied rooftop photovoltaic solar (that spins your meter backward.) Some heat pump water heaters are much noisier than others- pay attention to those specifications. Some people choose to install it in the garage to cut the noise factor, which in FL would still be pretty efficient for heating the hot water but in a garage it would have less effect on the reducing cooling load to the house. (Air Tap's ATI-xx water heaters are quieter than some of the others, but are 2x the cost of the more common GE GeoSpring.)

If you still want go solar-thermal for offsetting the domestic hot water energy use a batch type hot water heater that has no pumps or moving parts is both more reliable and lower cost.

FL has some of the best insolation, but not the greatest utility regulation policies regarding small distributed photovoltaic installations. FL doesn't allow third party ownership of rooftop solar with power purchasing agreements, though they do allow some types of lease options. For now FL still allows net-metering (running the meter backwards), but it is under constant push-back from the utility companies- evaluate any PV option carefully. This is an ongoing saga: http://www.solarsouthwestflorida.com/net-metering-under-attack-florida-spared-for-now/ The good news is that PV is getting cheaper every day. In less than five years will have a lifetime cost well below the residential retail rates in FL, if the projections of the banking sector and solar industry prove out.

So if not now, keep an eye on that market. When grid tied PV breaks $2/watt on the way down it's a better deal than buying from the utility almost anywhere in the US, with or without subsidy, as long as you're allowed to net-meter. It's $3-4/watt now in many parts of the US. According to NREL, the break-even point for un-subsidized grid-tied PV in FL happens at about $2.50/watt:

https://openpv.nrel.gov/breakeven ( It varies by county/utility click on the state to see the county-by county map. There are several locations in FL where break-even occurs well abve $4/watt. In Orlando's Orange County they're suggesting $3.68 is roughly break-even.)

If FL had state wide policies to better promote privately owned distributed generation it could become a solar power leader, but they're really trailing the pack in the sunshine states when it comes to implementation. It's telling that FL has only about 10-15% of the total installed PV capacity of a less populated, much less sunny state like MA, an artifact of differences in state utility regulation & policy. (FL has nearly 3x the population, and nearly 2x the annual insulation of MA.)

Pool heating is hardly necessary in that climate- a pool cover to limit evaporation and keep it clean is worth it though. Even a solar pool blanket would likely lead to an excessively warm pool in summer. Spend the real money on highest efficiency pool pump/filter systems instead.

Heat rejecting windows are more important than adding more insulation. Not all double pane low-E windows are alike. Hard-coat low-E coatings (the cheapest and most common low-E glazing) still have fairly high solar heat gain coefficients (SHGC- it's listed on the window spec). Soft coat low-E delivers much lower SHGC.

Hard coat low-E is fine on the south facing windows, since that gain is beneficial during the heating season when the sun is lower in the sky. Using roof overhangs or awnings to shade those windows is a better approach than trees, since during the summer it shades the window, but allows some gain during the heating season. The real energy-pig windows in a cooling dominated climates are the east and particularly the west facing windows, since the sun is always low when shining on those windows, maximizing the heat gain. The west side is more important than the east, since the gain occurs later in the day when the house has been soaking up heat all day, driving the PM cooling load peaks sky-high. If you're going to plant trees, plant them on the western and eastern sides of the house. If the roof overhangs don't shade the south windows adequately, install awnings. Exterior shutters or shades (Coolaroo or similar) are sometimes the "right" solution to west-facing window gains.

If the windows are clear-glass (not low-E) the SHGC is too high, but you can boost performance considerably at a much lower cost than replacement windows using low-E storm windows. Low-E storms only come in the hard-coat flavor (the lower gain soft coatings are too scratch prone), but it's still a big step in the right direction.

Air leaks at windows & doors are of much lesser importance than air leaks at the ceiling/attic-floor level, but still important. The outdoor dew points in FL are fairly high 4-6 months of the year, so even when you don't have a sensible (temperature) cooling load, the latent (humidity) load is still pretty substantial.

At 16 SEER the basic unit is better than code, but if the ducts are up in the attic above the insulation it's performance as a system is going to be pretty pathetic due to the high direct heat gains from the ducts and the high potential for air-handler driven air infiltration. Duct sealing is important, as well as air-sealing all of the duct boots to the ceiling gypsum. Air-sealing the attic from the outdoors and insulating at the roof deck with open cell spray foam may be called for, or not- it really depends. It's probably at least 2x oversized for the actual loads too, even before you tighten up and fix any of the easy solar-gain issues. When it's time to replace the AC, right-sizing it with a continuously-variable-speed or 2-stage heat pump unit will probably be worthwhile. If it's a fairly open floor plan, using high efficiency ductless mini-splits might make sense as a cheaper and even more efficient option.