Im not sure if all or some 9mm mags need a mag block or not. does this dsa 9mm ar15 mag need a mag block? Can anyone tell me? Will it function fine if I just put this mag in the magwell w/o a magblock?

Looks to me like the Promag 9MM AR magazine and that requires the use of a magblock.

I'm pretty sure the only 9mm mags that don't need a mag block are the Oly's, and they have what is in effect a mag block welded to every mag.

that must cost a lot if every mag needed a mag block. I plan to get a RRA mag block and use promag 9mm mags. First, I want to look at the magblock that takes original sten mags w/o modification. Who sells the sten magblock design? whats the difference between bottom-loader and top-loader magwells? Also, Is this the new RRA magblock or the older version? Does anyone make a 9mm lower that doesnt require any stupid magblocks?

I do believe that all of your questions could have been answered if you read the sticky at the top.  Anyway, if you purchase a Colt/RRA type 9mm set up then you need a mag block.  These set ups can use stock Colt (expensive), modified Uzi (cheaper), or promag (cheapest) magazines.  The main difference with top and bottom mounting blocks is that only bottom mounting blocks will operate the bolt hold open on the Colt or Promag mags (Uzi's don't use BHO) with the exception of the Hahn semi permanent top loader wich will engage the BHO.  If I've mistated anything than someone will be along shortly to correct me.