I guess your also looking to make sure one has the barrel shroud also.
You have a few options,
1) go with the two you found, its apperance is what your going for
2) Go without the barrel shroud, it make not look like a rifle, But unless you use the shroud it ends up being something which you have attached to your barrel for no real reason
Between those two there are 100 more sub-questions and what-not.
Does the shroud which you have on the stock barrel come off?
If so just grab a barrel and throw it over, saves money and keeps your stuff nicly organised
if that is the case, generally the longer the "control bore" or the "back" of a barrel ( even in one peice) the better, 1-2 inch bores with a 14'' of huge barrel wont work as well as a 8'' bore then 6'' of oversized barrel.
Blah blah blah im going off on a tangent, excuse my seemingly aweful post orginasation. Its the first post of Today and I get my Calc Exam mark in two hours.