Athlon 760k, Socket FM2+
£38 budget, no more, no less. Thermal paste is not needed (I can borrow from friend)
Its only a 100w cpu go and grab a cooler master hyper 212 evo if you have room for it in your case.
http://www.amazon.co.uk/Cooler-Master-Hyper-212-120mm/dp/B0068OI7T8 £25
Are there no better ones in my budget? Also, if I'm to buy an extra case fan for my Aerocool DS Cube (it has 1x200mm and 1x120mm already), which one should I buy? I was thinking of spectre pro by BitPhoenix.
That one will cool your CPU plenty, although I would advise getting a replacement fan for it to reduce some of the noise, Noctua fans are excellent
Do I need to buy separate stuff for cleaning off the previous thermal paste :(
Use isporopyl alcohol and some lint free cloth, thats the best way to ensure that you remove everything, although some people claim to have good enough results from just ribbing it with a cloth, I wouldnt personally recommend that though