For me it would be a good deal. It really depends on what you want. Some people prefer the heavy barrel (6601) and some people prefer the A2 style barrel, (6551). I prefer the A2 style and I also prefer the lowers that have the mag fence and small pivot hole. The deal is especially appealing since the 6551 is in "new" condition vs. your old "like new" rifle. I think I would have done the same thing. Of course, in reference to the lower, some would argue that "a lower, is a lower, is a lower."