I checked out the ad, the rear is just a stock D44 with posi-lock, non-rubicon - worth about $900 since you'll need to gut it and get lockers for it - if it's not bent. What the OP has now in his Rubicon is much better.
If the plan is to just upgrade your front axle, I'd go with a new housing swap your components out and sell your housing. As new as it is, you can probably get $1200 just for the housing.
if the plan is to also regear, you would only have the cash to regear both front and rear if your budget is the $3000 range.
Get a price quote from a good shop to do the complete swap and regear (if that's your plans) while it's apart. If you can have your empty housing sold before, you may be close to the $3000 mark for everything done - mine was about $3100, this is cost of axle and complete swap, just too bad I can't sell the old housing, I had it sold before the wreck.
Off Road Evolution has a $999.99 regear special - that's a good price.
