Tanks for the update.Q.
Which i5 CPU do you have?
What brand/model case do yo have? Will it take a ATX board? Can you add addition fans?
For your needs, the system will be firstly dependent on the power of the CPU, then RAM, then HDD configuration, then the GPU.
Please consider upgrading the parts below and keep using the GeForce GT610 and see how the system performs.
My first choice is the Asrock MB. > http://www.flipkart....BDDAMFF5W2EZH9T
RAM. Recommend 2 x 8 GB, = 16 GB, 1.5 volts. You can probable find cheaper than listed but stick to a well known brand. Let us know your choice so we can check compatibility
HDD. Recommend a new drive for the OS and programs, partition the existing drive for DATA and backups. Depending on what software used? more HDDs at a later date would speed up the work flow.
PSU. A selection of good quality ones, Please do not be tempted to skimp on this item.
Your MB will come with 2 SATA cables, HDDs usually ship without cables, please make sure you will have enough if you have more than 2 drives, including optical drives.
I always install a mini internal system speaker like this, > http://www.cwc-group.com/casp.html
As you will be removing the CPU and heat-sink it is important that all old TIM is removed from the CPU top and the heat-sink bottom, then new TIM applied as per the instruction. You will need the following.
I am sure you will be able to find parts cheaper than listed, suggest looking on Amazon for the RAM as international shipping would not be high as it is a light item.
Let us know what you think.