The only symptom I'm aware of is total system failure under load, i.e. completely crashing when you try to do anything significant. When you try to draw too much power, things don't just slow down, they MELT down.
Just checking the specs of your equipment though, it looks like the CPU and GPU are using more than half of your PSU wattage. If you intend on upgrading your GPU any time soon, you will almost certainly need a new PSU as well, and 'top of the line' is affordable for those - ~$100 for a 1000W PSU which will probably be more than enough for you for a long time.