Theres two little thumb screws on the carry handle that you can unscrew to reveal a Picitany rail for optics(scopes and reddots). This will not let you clear the front sight though. For that you need one of these:
http://www.airsoftsmith.com/store/product_info.php?cPath=30_80&products_id=588I would also invest in a better reddot than the one you linked. Theres many options but im pretty sure that one has paralax(a friend bought it a long time ago). Paralax is where the dot moves with you head, instead of staying in the same place... This means you will never have a true zero which means the shots will not go where the dot is...
I would recomend this one or something by the same company if you like reddots:
http://www.airsoftsmith.com/store/product_info.php?cPath=30_80&products_id=391Anything from G&P is a quality product. Same with G&G.
I don't really have any experience with D-Boys, I haven't heard anything really bad about them(besides the occasional lemmon) so I doubt you wont be satisfied.
If you have any other questions just ask, we have alot of experienced players on the forum that would be happy answering them.
sticks