I used to use Avast and it turned out to be causing my PC to take ages to boot up

IMO Microsoft Security Essentials is better

old card: Radeon 6850

new card: RX 580

I use this benchmark software https://www.passmark.com/

CPU is i5 3570K 3.4Ghz (unclocked for the tests)

The 3D tests on the newer card are a LOT bet ...

but even if it is stable won't higher temperatures lower the CPU's lifespan?

i5 3570K
Nero 3 CPU cooler with Artic Silver premium thermal paste

I overclocked it from 3.4 to 4.1 using the multiplier.

I ran Prime95 and after 10 mins the temperatures for each core are bet ...

so my GFX card came but when it came to installing it it turns out my PSU doesn't have the correct power cable for it (my new card needs one 8-pin connection, current card has two 6-pin connections). ...

Can I also ask if it is ok to mix branded and unbranded RAM sticks? Does it matter if two sticks are Corsair and the other two are unbranded as long as speed/capacity etc is all the same?

Current specs:

Asus P8Z77-V LX Motherboard
Chillblast Vantage Black Midi Mesh Gaming Case
Intel Core i5 3570K @ 3.40GHz overclocked via multiplier to 3.9GHz
Nero 3 CPU cooler with Artic Silver ...

So say I decide to upgrade my PC and put in a new video card and RAM then attach a bigger and newer monitor, but keeping the same PSU.

What happens if I then turn the PC on and the PSU isn't good e ...

So I set the BCLK back to 100 and upped the multiplier from 34 to 39.

System and temperatures seem stable enough, is there any need to alter the voltage or is it really as simple as upping the mult ...

https://www.amazon.co.uk/Dell-S2417DG-Widescreen-Monitor-2560x1440/dp/B01KZIOSSQ?psc=1&SubscriptionId=AKIAJV4KMHBMUG36SMIQ

I think 27inch is a bit physically big for a monitor, what do you thin ...