If you were in a "single" relationship - not necessarily "mono" (but could be) - but happen to go from zero relationships to one relationship - would it be bad/wrong/offensive/creepy to say that THAT RELATIONSHIP has "enhanced" your life? Same shit, different day.
I agree with nycindie that a person's attitude and motivation (or a "couple's" attitude & motivation, for all those unicorn-hunting "poly-couples" who come on here and declare that they are "one person romantically" and want to "add a third to their relationship" - "a" third???? SERIOUSLY??? and you wonder why people mock you?), is very relevant when it comes to the quality/type of "enhancement" that an additional relationship can provide to oneself.