Do Not buy anything if you can get for nothing all the security you require.
You only need to have a single Anti Virus programme and also a single programme to protect from Malware. However you appear to have already more than you require and I am surprised if you are Not having problems from conflicts of programmes.
My advice would be to forget about purchasing Kaspersky and get shot of Spybot. The reason I suggest you remove Spybot is because it messes about with Windows Registry and, in my opinion, could do more harm than good. I always tell folk to stay away from Registry Cleaners/Repairers which can cause irreparable damage to a computer.