I'm sorry I'm catching you a bit late Abhi. But for IM purpose do you have anything specific in mind ?
The first thing that strikes me for IM purposes is RAM. Because how poorly Firefox, Chrome are managing the RAM, I would give it a boost.
With a $3K budget you could go with a 32 GB DDR4 PC.
You might think it is too much and most of people will not agree with that. Yet, here I often go to the 24 GB of usage and sometimes more without running something specific (lot of small apps) and the pagesys file is disabled on the PC has well to save some write / read operations on the SSD to make it live longer.
The 8 GB free RAM remaining are pure confort.
CPU wise, I'm using this one for my office PC Intel Core i7-5820K, because of the 6 cores 12 threads which is great to do multiple tasks.
Don't fall for the Intel Core i7-5830K it doesn't add much but for gamers who wants 2 GPU.
No don't overclock your RAM, you won't notice a difference!
To choose a RAM you have 2 factors, it is easy. The frequency and the CAS (X-X-X-XX)
Pictures 4 circle, The frequency is the speed to go around the circles, while the CAS is the size of them.
So if you go with a lower CAS and slightly lower speed, it would still beat a higher freq. So pay attention to that.
Motherboard, I'm a Gigabyte fan and not much of an Asus one. But you know taste and colors..
That being said, I noticed that Gigabyte often have more features for the same price point. And, I had an Asus fried over a RAM Swap once so it doesn't get to receive my love

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