Don't even use the words "affordable" and "fine art" the same sentence. Paper is either a) acid and lignan free, cotton, buffered and hand-molded (and worth more than your camera by weight) or b) mass produced, with optical brighteners and anything but neutral in pH so that it will yellow if you breathe on it hard or look at it squinty (and worth 70% of the stuff that will bankrupt you). Someone should tell these guys that their paper does not actually contain a semi-precious metal or need to be produced in massive, dark light-tight factories, as they seem to have missed the memo.
For non-archival matte printing, I like Adorama's OEM white 8x10 card-stock. For glossy, I like Costco's Kirkland brand. For archival stuff, look at inkjetmall.com and see what Jon Cone is flogging these days.
Good Luck, despite my rant there are some very nice papers out there. Understanding how they each interact with ink would be a full time job.
Ben Marks