Because so many accuracy issues are connected to the forend. Many shooters are getting a dedicated forend for each barrel.
I haven't done this, but I feel it is a good idea. Since your just starting down this road. If your still set on a barrel only, this is a good option for you.
Personally, I would watch the classifieds and local GS walls. 223 handis are fairly common and not all that much more then what you will pay for your new barrel.
I am more of the opinion that we just forget about the switch barrel aspect and buy complete firearms. Less trouble overall.
CW