I'd like to comment that the monitor you chose is an excellant performer and one of my top picks. Why you may ask yourself? Well that BenQ has an incredibly low black level. One of the lowest black levels on all lcd monitors. Deep inky blacks makes everything else look much better and clearer none of that foggy greyish look in dark scenes when you watch a movie. That's an awesome monitor for watching movies and tv shows and youtube videos and for gaming on dark levels too. Deep black levels boost the contrast ratio significantly as well and that benq has one of the highest contrast ratios as well.
I agree with everyone else on the PSU. Really all you need is a 450 watt psu. The gtx 680 actually uses much less power then most flagship cards have lately.
Replace external dvd with internal as they are cheaper and a direct sata connection performs better than a usb 2.0 connection.
Also since you have an SSD it is really not needed to have a 7200 rpm hdd. Save some money and go with the western digital red drives. They feature 1TB per disc density so even though they are slower rpm the higher density makes back some of the speed and they are cheaper than black and they are durable and meant to be ran 24/7 in a NAS box. If you don't mind a little less performance you could save even more money going with a WD green drive or upgrade to a larger size for the same price as the lower size black.
Your OS and all your important programs and games will run off the ssd. All the media you store on the HDD will run the same off a slower rpm drive. Save the money or get a larger HDD for the same price.
You should also think about saving 100 dollars and getting a gtx 670. The gtx 670 has 90%+ the performance of the gtx 680 and it puts a benjamin in your pocket. The GTX 670 is the closest a step down card has been in performance in relation to the flagship in a long while. It's going to run anything you throw at it nearly identical to the gtx 680. If you will be gaming on just that 1080p benq monitor the gtx 670 will allow you to play every game at ultra settings at 1080p resolution no problem. Save yourself the cash.
GTX 680 is going for 405 [wow thats a really good deal]
http://www.newegg.com/Product/Product.aspx?Item=N82E168... (generic stock card at 2GB) to 600
http://www.newegg.com/Product/Product.aspx?Item=N82E168... (incredibly high overclocked custom card)
GTX 670 is going for 360
http://www.newegg.com/Product/Product.aspx?Item=N82E168... (2GB stock clocks and board) to 450
http://www.newegg.com/Product/Product.aspx?Item=N82E168... (2GB super fast oc even faster oc then many 680's)
That 1 gtx680 for only 405 is messing the comparison up as usually gtx 680's are not that cheap. That GTX680 for 405 is an incredible deal. It may not overclock the highest but for that price wow.
Do you plan on overclocking? If you really want to overclock and experiment and that's important to you I highly suggest the swiftech h20 x20 self contaiined water cooling system. It costs 220 dollars but it blows away all the competition except advanced multiple loop water cooling setups. And it's just as easy as setting up a corsair self contained water cooling. If you care a little less about overclocking but still want to then you could pick a corsair h100i for 115 or an h80i for 100. If you don;t care about the corsair link monitoring built in you can get the h100 for about 85-90 or an h80 for 80-85 and still be able to overclock nicely.
If you aren't going to overclock then the cheaper cooling you have selected is fine.