One advantage of a modular PC is that fixing a broken one can be much cheaper if you can pinpoint which component is broken. It also helps a lot if the perform

One advantage of a modular PC is that fixing a broken one can be much cheaper if you can pinpoint which component is broken. It also helps a lot if the performance and requirements change at different speeds for different components. For a gaming PC you'll upgrade the GPU more often than you actually need to upgrade the CPU and the rest of the system. My 4 year old CPU is still fast enough (i2500k), but I upgraded the GPU in the meantime and added an SSD. Reusing old parts can be pretty cheap, but probably doesn't make all that much sense if you need parts that aren't in common use anymore like the DDR2 in your case.