Welcome.
[General statements follow - not specific to a 1999 Liberty RX]
The stock intake system is known to be pretty good up to a pretty robust power level. Of course the need to modify, have better sound, etc. is valid - it's your car.
If you change the diameter of the pipe containing the MAF sensor the car will need a re-tune, so factor that cost/complexity into your plans & decisions.
As Stifull noted above, there are a few options (DIY or off-the-shelf) that involve pod filters. Performance on a low-power to medium-power car would probably not improve, but could get worse if you're drawing hot engine bay air. Of course, if you want the look and sound and don't mind lost performance then have at it.
On my SH Forester I removed the "milk bottle" and extended the secondary airbox intake to the front of the car (see link below).
viewtopic.php?f=10&t=36234&start=15Since that was posted I've removed the last piece (the forward-facing silicone 90-degree piece) to have better access to the tow hook for motorsports days and to reduce the amount of grit that ends up in the air filter. Less "ram-air effect" but easier to live with.