umm... you will also need an Amplifier for your sub. Subs draw a TON of power... Unless you have a sub with a built in amp.
If it doesn't have an amp, you need a crossover, and then a monoblock single or dual channel amp. Depending on the size of your sub, is dependent on the amp that you need for it. Since this is in the Getz forum i'm assuming it's not going to be any bigger than 10in, so a 1000W dual channel will do the trick.