Most of us here aren't fans of using acrylic or Plexi tops in blocks. There have been MANY discussions regarding these. One of the main concernes is that these types of blocks can be cracked pretty easily if you use metal barbs. In the process of tightening the barbs, you apply stress, which in turn can cause it to crack, or in some cases may wear the threads down and not created a good seal on the barb, resulting in leaks.
That's not to say this happens with all acrylic/plexi topped blocks, or that blocks using this material are crap. Just be forwarned, that special care shoudl be taken with them, and plastic barbs would be recomended.
That being said, When it coimes to GPU blocks, honestly, just pic one you think looks cool (form a good manufacturer). When it comes down to it, the difference in performance bettwen any of the blocks out there will be nominal at best.
I personally, am not a fan of the full coverage blocks. They typically aren't portable to another card. So that block will probably only work with that one card. If yo uwant to "future" proff yourself, the GPU only blocks are the way to go. They cna be used on different cards, so in a year or two, you can use that block again on yor next card (most likely, unless NVIDIA comes up with some whacked out new hold down scheme).
The full coverage blocks are also pretty big, and don't always make good connections to the ram. IMO yo are better off passive cooling the ram, and going the GPU only route.