Hi Firstly I would like to say that I'm novice to this so tell me if I'm wrong. I'm have been using Yamaha AS-500 connected to pair Wharfedale diamond 10.4 and everything was just fine. Yesterday I went shopping and have seen a pair of Wharfedale 9.0 for £40 clearance so I could resist those as I have read some good reviews about them before. I connected those to Yamaha AS-500. So now I have 10.4 as fronts and 9.0 as back. Everything is just fine they giving good sound for the money but my amp get hot after 10min of use at about 50-60 max power. Where I had only 10.4 before playing that loud and everything was just fine. It is my first proper system which I bought two weeks ago so I don't know if it's normal or no. I'm using different cable to connect my front and back speakers but they both are speakers cables and has been recommended in store so I don't thing it's an issue. Also I would like to add sub to my system but now I'm not sure if my amp can handle it because it's might get even hotter. thanks for help.