What is the best value for stevia extract powder?

I just looked through the discussions on “stevia”, and I didn’t find any recent responses that compared different brands and how well those particular brands taste in tea.

Years ago after doing some searching on the best value for stevia I found that the extract powders were the best. Then, after having tried stevia extract from Trader Joe’s, NOW, and KAL, I found KAL to be the best bang for the buck (buying through Amazon); Trader Joe’s Stevia was reasonably sweet and tastes good but is a little more expensive then KAL and NOW; I found the NOW brand to be cheaper than the KAL brand but not nearly as sweet. So, we have been using the KAL Stevia extract for years; but recently KAL made some changes to it, and the reviews on Amazon make me wonder if the changes will negatively impact the taste in beverages, like hot tea. Often the reviews have a general focus are and not specific to their use (i.e. baking, iced tea, hot tea, coffee, etc.). I was wondering, has anyone out here tried the newer KAL stevia extract, specifically in hot tea, and if so do you find it to be any different than the older stuff?

I went ahead and bought these three stevia extract powders and plan on doing a taste comparison (in my tea) after I get them all:
http://www.moodandmind.com/stevia-extract-powder-free-micro-scoop-100-pure-4-oz/
http://smile.amazon.com/gp/product/B000VRSR84/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
http://purebulk.com/stevia-extract-powder-90/

Also, I found the Nuts.com stevia powder from one of the discussions and was wondering if anyone uses it in tea and if so how potent it is.

I was also wondering if anyone uses any other brands of stevia that wants to offer any feedback on the taste (in hot tea) and value (sweetness per serving).

Thank you for any input.