An IFS lift will hold up fine providing you leave your ego on the pavement. I have had the same IFS lift on my '90 going on 12 ys now, and I wheel in the rocks. As long as your are nice to you don't abuse your rig on the trail the IFS will/can hold up. Granted the IFS can't wheel the rocks as well as an SA rig, but for a DD, that spends most of its time on the road, it is best to keep it IFS, until you are sure SA is the way you want to go.

You could easily run 33's with BJ spacers and a 2" BL, rebuild the rear springs, which will cost about $250. Several here like the 5.29's for 33's(you will need them for 35's), so you should go ahead and install the 5.29's now. You could get a rear ARB/5.29 equiped diff anywhere from $1150(DavezOffroad.com) up, and you can usually find 5.29 equiped IFS difs for about $2-250. This still comes in shy of the $2k you have set aside for the SAS or IFS. The rest of the money for the lift could go to dual T-cases, need anotehr $3-400 or so for driveline mods and dual t-case x-member.

Pick up a welder, take some lessons, fab up some sliders and bumpers to help your welding skills, for the eventual SAS if and when you feel the need.