I have the select tech's and love them. I have only looked at the power blocks at Dick's sporting goods so have no real opinion on them. The select tech's have a very sturdy build and are very simple to change the weight. I use them for p90x and have been very happy with them. If you check craigslist often enough you should be able to find a pair used for a reasonable price if money is an issue since they are about $100 more than the powerblocks. You just have to check pretty often as I found the ones listed sold in a very short amount of time.
French writer Alexis de Tocqueville warned about when visiting this fledgling democracy in the early 19th century – that this "American republic will endure until politicians realize they can bribe the people with their own money."