Calculation of time needed to crack DES with my CPU
I can't provide you with good numbers without actually benchmarking on your system.

All I can provide you with are estimates, based on the fact that Serpent is roughly as fast as DES. Of course the figures I can give you aren't actually brute-force figures but rather how much data can be encrypted per time, but this should give a solid estimate of the required time.

The general approach is to measure how many keys per second you can try and then divide $2^{56}$ by this number which will result in the number of seconds you'll need.

So let's estimate for Serpent with 56 bits. Serpent can get up to 0.16 GB/s on your machine as this is mainly computation bound. 0.16 GB is roughly $2^{24}$ blocks for DES, meaning you can roughly try $2^{24}$ keys per second. This means you need $2^{56}/2^{24}=2^{32}$ seconds for this which is equal to 136 years.

I'm sorry but I doubt this is feasible for you.
Note that even the brand-new Intel Core i7 6700K can only do 0.47 GB / s meaning an i7 6700K would also still require roughly 45 years. And to get even more crazy: the Intel Core i7 5960X is the best consumer CPU as of now can only do 0.63 GB / s resulting in 34 years. Now finally consider the currently strongest possible server mainboard running 8x Intel Xeon E7-8890v3 with 18 cores. There's no measured benchmark out there but I assume the performance to scale linearly with the number of cores (75 MB/s per core) and the frequency (62.5 MB/s with E7's freq). This would mean that this board could do 9GB / s of Serpent meaning $2^{30}$ blocks and thereby $2^{26}$ seconds being equivalent to 2.12 years (however this board would roughly cost $56k in 2015).