I agree with Sarah - pay special attention to the things that can't be added afterwards.
Take the furnace: If you ever plan on camping during the winter, traveling across the US, or are interested in resale value, you may want to consider it. Keep in mind that a Camp-Inn should last 30 years, and a lot can change in that time - including where you live. Here in the NW, the heater effectively doubles our 560's usefullness.
Solar Hookup: This option wasn't available when we bought our 560. So, I added my own roof-mounted panel later. If I purchased today, I would have Camp-Inn mount the panel for me - this way the cabling to the roof could be 100% hidden. I LOVE solar - it's free, endless power. We don't have the fridge, so I'm not sure how a panel would keep up with it, but our panel will run everything else. So, at the very least, get the solar panel hookup - but this will really only work with an external solar panel, like a tripod mounted setup. Some people prefer this because it can be positioned to catch optimum rays from the sun. I didn't want another thing that had to be hauled around and setup, so I just went with a permanently mounted panel that was 2x bigger (85w). Search for 'Solar Project' if interested in seeing photos.
AC: Probably a must for you - just remember that it is the ONLY thing that won't run off of the battery.
SUV Package: Unless your wife is very short this is a no brainer.
Handicap Access: Lots of old folks have teardrops - only a few have or need the handicap access. From the looks of your photo, you must be planning WAY ahead. I'm pretty sure this could be added later as needed - Cary would know for sure.
We got the 15in TV for our daughter as well - before there were iPads. Now, I'm not sure if we would get it again. Sure we use it, but we will still have our trailer years after the TV/DVD player is obsolete. It's a matter of convenience versus Moore's law.
Internal Batter Isolator: get it.
Stainless Bumper: Why not - you're already getting most everything else.
Galley Windscreens: Very good option, but it can be added later. I would get it unless you've got to find a way to keep the price down.
Electric brakes: Pretty much a must if you are towing with a smaller or medium sized car or SUV. We didn't get the parking brake because I couldn't justify the extra cost when a pair of chocks would do the same thing.
Alcan Cover: We originally purchased this, but later returned it unopened because we store our trailer in the garage. This is the very best place for your 560. If you can't put it in the garage, then get the cover.
Side Tent: We started out with one, and then upgraded to two. But, lately, we haven't been using either. Nice for extended stays or bad weather - but, as we get better at camping we have been using it less. This is one thing you can always add later.
Hi-Lo Mirror: Just got it, and I think it's great. But, again, something that can be added at any time. In fact, it might even be better if you add it yourself, because the standard location for the mirror might be too low for you.
Door screens: Get them, especially in Texas with all of your warm weather.
Receiver hitch: We have never used ours yet, but I'm still glad we have it. Some day we might haul bikes or gear with it. I wouldn't want to try to add this myself later.
Fridge: We didn't start out with this - just the cooler. Perhaps we'll add it later. It will be interesting to see if my 85w solar panel will be able to keep up with it. You can always add this later.
Sunroof: Make sure you get the Fantastic Fan. This is more important than the sunroof. With that said, you can have both on the 560. The sunroof is perfectly positioned to let you look up at the stars at night. We love it.
Get the cup holders for the cabin.
After you purchase, you should probably look at the McNugit knife block and cBallen's undercounter storage bin dividers.