For a $600 budget, it would be difficult to play games like Watchdogs while having the CPU power to emulate. This build is in your price range, but it only has 4GB of RAM, and the GPU is only a GTX 750 (might not run modern games well). The CPU is still a Haswell. You can't beat them for gaming, and especially for emulation. This will run most games smoothly on Dolphin, but might not run graphic-intensive modern games as well.
http://ca.pcpartpicker.com/p/3Con8
You can drop the optical drive, unless you will absolutely need it. Nowadays everything is on USB flash drives, and yo can even use them to boot an operating system. If you skip out on the wifi card, you could go for a cheaper mobo as well. With 4GB of RAM, no optical drive, no wifi card, and a $45 mobo, you could get a better GPU on the spot. This will allow more modern games to run smoothly compared to the first build.
http://ca.pcpartpicker.com/p/3Co6T
I don't know of your financial situation as to why you can't upgrade later on, but it is honestly the best decision. The integrated Intel HD Graphics 4600 are enough for Dolphin, and they are decent in most other areas. You can try it to see if they run modern games and your desired resolutions, and you can upgrade to a dedicated GPU later on if you would need to. Assembly is not too difficult (just plug it in and screw it in place). This will allow you to have more optimization options, such as a higher clocked CPU, a case of your choice and more storage/memory/expansions.
One final note: check if your $600 coupon thing is able to use price matched prices from Memory Express. Their policy of taking 25% of the difference off of the matched price can help save quite a bit and will allow you to use better components. Also, check if the coupon thing includes taxes or not.
http://ca.pcpartpicker.com/p/3Con8
You can drop the optical drive, unless you will absolutely need it. Nowadays everything is on USB flash drives, and yo can even use them to boot an operating system. If you skip out on the wifi card, you could go for a cheaper mobo as well. With 4GB of RAM, no optical drive, no wifi card, and a $45 mobo, you could get a better GPU on the spot. This will allow more modern games to run smoothly compared to the first build.
http://ca.pcpartpicker.com/p/3Co6T
I don't know of your financial situation as to why you can't upgrade later on, but it is honestly the best decision. The integrated Intel HD Graphics 4600 are enough for Dolphin, and they are decent in most other areas. You can try it to see if they run modern games and your desired resolutions, and you can upgrade to a dedicated GPU later on if you would need to. Assembly is not too difficult (just plug it in and screw it in place). This will allow you to have more optimization options, such as a higher clocked CPU, a case of your choice and more storage/memory/expansions.
One final note: check if your $600 coupon thing is able to use price matched prices from Memory Express. Their policy of taking 25% of the difference off of the matched price can help save quite a bit and will allow you to use better components. Also, check if the coupon thing includes taxes or not.