The stuff you are looking at is 0.0625" thick which is about three times thicker than what you need it to be. You will not be happy trying to thin that stuff down to the 0.020"-0.025" range.
If you want to compare steel properties, there is a pretty good tool here:
http://zknives.com/knives/steels/steelchart.php You can select metals from the chart and graph the properties to give you a quick visual comparison.
In my humble opinion, the best cost/benefit ratio is achieved by using feeler gauge stock. Lately I've been using Starrett brand because I came across a couple of good deals on ebay but I have also used Precision brand and I can't notice a difference between the two.
I'm sure there are people here who have had success with other metals as well. I've just mentioned what I like best after having tried many various metals which includes hacksaw blades, reciprocating saw blades, band saw blades, wiper inserts, street sweeper bristles, sink snake, kitchen knives, and probably some other random metals that I am forgetting to mention right now. I will say that sink snake gets an honorable mention but you have to be aware that it is spring steel so it has a bit of a different feel than more rigid metals such as those that are used for feeler gauge. Here is a link that will show you what the package of the sink snake looks like:
http://compare.ebay.com/like/250559533337?ltyp=AllFixedPriceItemTypes&var=sbar&rvr_id=217313743740&crlp=1_263602_304662&UA=L*F%3F&GUID=8384f6d612e0a0366160b2f0ffbe7c6e&itemid=250559533337&ff4=263602_304662, but you can get the stuff at Walmart. If you are new to pick making, I would suggest using this stuff first as it is very easy to work with and it makes good quality picks.