A spool will make for tricky street driving during the FL rains. A Detroit would be a decent second choice...but if you are planning on switching to 31 spl...you are going ot have to buy it, so theres $400-425...plus axles, gears and setup...You are at a grand give or take a few bucks...for $250 more you could have the ARB. When you are talking about $1K, whats $1.25K, really; sure its 25% more. I would save a few more months and not settle.
There are some who say a locked rear is more beneficial than a locked front...others argue the opposite. I would think that it is cheaper and easier to later swap in/build a new 3rd member than it is to build/setup a D44. I would go ahead and get an ARB for the front, set it up the way you want--presumably with 4.11s (maybe new HD shafts, which are a good idea with a locker and anything bigger than 33"s). You can probably find a cheap, open, 4.11 geared 3rd member to match the new front for now (28 or 31 spl--if its a 28 spl run stock axles for now; if its a 31 spl you come across, go ahead and get the Yukons). This way you can still drive it without sinking $2K into the axles. You may decide this this setup provides all the traction you need and that you dont need to do anything with the rear end. If you decide you need a stronger rearend, you can save for a little while and then have your old 3rd member built with the ARB and new gears, etc...
The reason why I argue it this way is long term spending. Sure you may front $150-200 for a used 3rd with 4.11s, but that can be turned around for what you paid once you build up your old 3.50 geared 3rd with the new stuff (in a year or so)...no net loss. If you ARB the rear first, you still have to regear the front. That means you have to put a new carrier up front now...since you presumably want some kind of traction device up front, it means you have to settle. OX is just as expensive as an ARB. The Aussie is supposed to be OK, but in the end it has the weaknesses and negs of any lunch-box style carrier...and there are the drivability issues that can arise in wet, icy conditions if in 4WD... so, spend the money right up front just once! An install (labor at most 'shops'), unless you have good friends who can do it for beer (=almost free, unless they are slow and thirsty), will run you between $300-500 to install the locker and gears for just the front...you dont want to do that twice. Finding a properly geared 3rd member is much easier, can be swapped within minutes and keeps more $ in your pocket until you are ready to spend. This way, you end up with a selectable up front right off the bat. If you need traction, lock it, if you need 4wd in questionable weather, leave it open. The cost of adding air is not very much--whether you use a small compressor or a small CO2 tank, its about a wash.