I use a pair of tinted varifocals as my 'spare pair' and they do seem to give a little better definition in marginal conditions, but not to the extent reported by DB. Sounds like you've hit the sweet spot with those, and a LOT cheaper than another pair of specs!
TOO
ps
Many years ago, a flying friend of mine was asked where his 'spare pair' were. He said 'oh, it's all right, I'm wearing them'. Nothing more was said...