Hi, New to this and excuse my lack of knowledge. I am learning. Right, I have 2 Max 600w speakers and an SPL 2 way Amp. I would like to add a sub. Will I need a new Amp to produce a 2.1 system? I want a wired sub. Any suggestions for what Amp I will need to power my 2 existing speakers and to add a wired/powered sub? I have a budget of £400. is this enough? It is for home use only. Many thanks In advance.