This is tricky and I think Montana has given a good answer. UK auctions frequently offer "action and stock only" of guns having barrels beyond reproof (usually thin or damaged). The estimated prices of these guns appears to make them a bargain. However, one must be very careful what the gun will be worth if rebarreled. Sometimes the original barrels can be released to a gunmaker for repair, in which case sleeving or lining is an option.
So, Mike, to address your question a bit ore directly, lets assume that your A&N is an original quality grade 3 (about like a Scott Monte Carlo "B") and in current condition of heavy use, but no abuse. BV3-OQ3-CC$ = $4200. As "action and stock only", maybe $500. I'd say the new barrels have about equal value to the gun as good original barrels. However, as guns are found of higher and higher current condition, the new barrels subtract from originality and become a deduct. Were you to find a gun similar to yours in pristine condition, BV3-OQ3-CC1 = $10,500. Now, suppose we find the pristine gun that had the barrels run over by the "pickers-ups'" truck the first time it was out hunting and the owner was so utterly disgusted that he simply put it away (properly wiped and preserved) and it has just now surfaced. OK, do we sleeve it or make new barrels? What is it worth sleeved and what is it worth with new barrels? Howz about some opinions?