Not sure if I'm missing something here but a 4" lift would be 1.5" taller than your 2.5" leveling kit. The easiest/cheapest way to raise it up to 4" would be to completely start over. Lower end lifts (like the one I have on my truck) such as Rough Country or Tuff Country are plenty good for most people out there for "normal" driving that you're referring to.
If you're looking to spend $2k+, you can significantly improve your ride quality by going with Icon or Carli. The springs and shocks are the nicer parts of these lifts and you can upgrade to those later if you start with a Rough Country lift.
If you buy Rough Country, buy directly from them instead of one of their vendors. The price is the same everywhere for their stuff. Ordering through RC will save you time and will be much easier to deal with if you have any issues down the road.
Use the search function on here and you'll find a ton of threads on this same topic. Lots of good info on here.
If you're looking to spend $2k+, you can significantly improve your ride quality by going with Icon or Carli. The springs and shocks are the nicer parts of these lifts and you can upgrade to those later if you start with a Rough Country lift.
If you buy Rough Country, buy directly from them instead of one of their vendors. The price is the same everywhere for their stuff. Ordering through RC will save you time and will be much easier to deal with if you have any issues down the road.
Use the search function on here and you'll find a ton of threads on this same topic. Lots of good info on here.