I think you could do much better putting one together from higher quality parts and not spend any more money, possibly less, for the same performance or better. I had an almost identical one on a previous boat. Actually, I still have it because I replaced it with a better one. I think the one that you are looking at from D&R is of very low-quality. I hated mine, especially the v-cleat. I recently replaced a 5 to 1 vang which I thought was barely adequate.
For ideas on how to make a vang from parts that will be more effective and easier to use, check out the moderator from the Daysailer one forum Phill.
gallery/search.php?user_id=66 Scroll down in this gallery and there are pictures of his set up. If you don't want to go to the higher purchase set up for vang sheeting you should be able to make something 8 to 1 pretty inexpensively. Placing the control cleat on the cuddy top is far more user-friendly.
I was able to purchase many of my basic vang parts from purchases off eBay, including shipping it was less than half the price of buying the same parts retail and they were all new. For me it was a fun project.