You don't need an expensive DVD drive , the one I listed in the list is only $23, you just need it to play music cd and if you have any DVD media on a disc. Some hardware has installation software on a DVD.
The small tube of Artic Silver 5 is only $9 and it's always good to have some on hand in case you have to remove the heat sink for some reason. If you have to remove the heat sink for some reason you have to redo the thermal compound with a fresh layer after wiping off the previous layer.
Adding a second video card is exactly for that reason , to increase FPS. Some games are so demanding on high settings that a single middle of the road video card will struggle and you end up having to lower the settings or resolution. So on the GTX 600 model line you have the 660, 660Ti, 670 and the 680 and with the newer 700 line you have the 760, 770, 780 and the Titan. Each of these cards will give varying degrees of performance and FPS in any given game. The higher and newer the card the better the game performance and then add o that multiple cards and you get many different levels of performance.
The power supply plays a key role here as the video card can draw a lot of Watts during game play and it also has to power the CPU , ram , motherboard and HDDs and fans. If there is any chance that you will add a second video card you can get a higher watt PSU now or buy one later to replace what you get now.
The parts that would be changed by an increased budget would be the video card , the motherboard and the power supply, the CPU would stay because it's the best that you can get at the moment and will give you the best performance.
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