I personally wouldn't pay the "Colt" premium pricing for a "Colt" marked tube.
There are a TON of barrel mfgs that make very high quality 9mm AR barrels, including but not limited to The Riddle of Steel (TROS), Spikes (Green Mountain blanks...if you can find one), Bravo Co Mfg (BCM), CMMG (WASP-treated/Nitrided), ADCO (Steve and the guys use a variety of different mfg's tubes, but the ones I have used have all been very good barrels)...there are others, but I am drawing a blank at the moment.
Also, there are a couple of "Colt" dealers on BARFCOM that might be able to get you a true Colt barrel if you really want to go that route...shouldn't be too tough to find with a simple browsing through the EE over there (there are regularly 9mm tubes for sale as well of varying quality/condition/mfg).
Finally, as indicated above, Steve and the guys at ADCO do VERY good work on barrels, including chopping your current Colt barrel down to your specified length and threading it for you. While they claim that cutting a CL'd barrel is no problem (and I have seen first hand ones that they have cut which look 100% to me), I am always a little edgy about cutting them for fear of f-ing up the chrome lining and having a ruined barrel. Just something to consider in the interest of full disclosure since your 6951 barrel IS CL'd.