It is normal for svchost to be running constantly after a fresh install of Windows as it has a large number of updates to do. That being said your CPU should not be at 100% with the CPU you have.
First of all I suggest making sure all your drivers are upto date, especially your motherboard and chipset drivers. Next I would make sure all the CPU cores are unpacked (read this: http://www.coderbag.com/programming-c/disable-cpu-core-parking-utility).
If that does not fix the high CPU usage then you likely have 1 of these 2 issues.
1. Your PC is infected with malware and the malware is disguised as the svchost process
2. You are suffering from the known issue where windows update uses large percentage of the CPU.
If it is one then you need to scan for and remove any hardware. If it is 2 then you could try installing MIcrosoft fix from here:
https://support.microsoft.com/en-us/kb/3050265 (goto method 2 and download correct fix for your OS [i have assumed you are running windows 7]).
P.S. I don't think you have an issue with RAM, it sounds to me like the issue is with your CPU and you will probably find that your RAM and CPU usage go down once you have full updated Windows. To confirm goto resource monitor (i put instructions in an earlier post), goto CPU tab and look for services, click on CPU column and it will organise services by how much of the CPU you are using. If the service using a large amount of the CPU is wuaserv, then this is the known issue I was talking about concerning Windows Update. Right Click it and select stop service. Now before you goto bed open power options in control panel and set your PC to never goto sleep. Now start windows update when and leave it running over night so it does not matter that your PC is slow. Hopefully in the morning it will have done a large chunk of the updates.