Mark, You might also try strings.com ... they have a decent assortment. I occasionally order from them and always have my order in a week (I live in southern Ontario).

Regarding flatwounds: I rather like the D'Addario "Flat tops" which are semi flat, quieter, smoother, and great for slide. I use them for my lapsteel set-up acoustic, and for recording if I'm concerned about string noise.

I agree with your remarks about discounts. Some stores offer a teacher or performer price, and so they should, we send alot of business their way. It's a happy partnership, or at least should be. I recommend the store and they reward me, simple as that.

A mandolin tip: I used to have an overly bright F style mandolin the sound of which I mellowed by changing only half the strings at a time...that is, one of each identical pair. Timing the change wasn't too difficult. It saved a bit on string expenses and improved the general tone of the instrument.