Steam version system requirements.

Alsmir

I have a rather unusal issue, which is performance issues... on my PC.

Lets start from the beginning:
I've been visiting my parents on weekends more often and I decided to play some MPQ while I'm there. I'm a Steam version user. I found my old PC (Dual Core 3GHz, 4 GB RAM, Radeon HD7770) and realised that it's struggling to run MPQ! Ok, fine, maybe that machine needs some renovations (it wasn't used for quite a while). I formated the whole thing, installed SSD and a fresh copy of system (Win 7 64bit). That made quite a difference for almost everything, almost.

Battles are running quite fine, there are some slow downs during massive cascades but that's it, however load times between screens are absurd (up to 15s). Minimal requirements on Steam state:
Intel Pentium 4 3.00GHz or better
1 GB RAM
Intel HD 3000 / Nvidia GeForce 8600 GT / ATI Radeon HD 4650

So what are the optimal requirements?

For comparison, I'm able to run on the same PC:
Civilization VI - no issues at all
Diablo 3 - flawlessly

I haven't tested recently with other games, but I used to run Arma 3 on this PC (low-medium settings), Battlefield Hardline (similar settings) and I never expected to have problems with MPQ.

Any advice?