Ha. I have a heat mat under the container I use to keep my feeder crickets for my geckos. I took them off heat so they were less active for my geckos to catch (I spoil them I know), and after about 20 mins 4-5 crickets went belly up. I then brought the heat back and within 5 minutes they were all behaving like healthy crickets once again. I never knew temperature could have such a rapid affect on them but this just proves it does.
From my experience of buying crickets in the past five years, Pieces have a steady supply of crickets, although they are usually sold with 1 or 2 different species of pests per tub (furry worm thing, spiders, zig zag flies etc). Their mealworms are well supplied but occasionally are out of stock. They also have pest species present (lesser mealworm, etc).
Biosupplies (recently purchased by Aquatic Solutions?) have a great quality cricket, very rare to see pest species present (in fact I cannot remember ever seeing any).
Amphibian Research Centre (ARC) average quality crickets, many pest species present.
Livefoods unlimited, I cannot comment as I have never seen their crickets however I hear they are good quality and they come recommended by many.
I would love to enter into the cricket breeding business, I believe there is still a market out there for good quality reliable crickets marketed properly. I just need a business partner and come capital 8)