I think we're missing some important questions here.....
What is your goal here? Earth shattering bass? High db (volume)?, clean balanced sound? Do you care about how much space in the hatch you are going to have available?
Help us out a little more with the model number of your head unit so that we can look some specs.
And Justin (Speedcheeser) is right. Make sure you have soldered your wires. When done properly, it offers the least amount of resistance in your wiring. Crimping is lazy.
Here are some DO's and DON'Ts for ya...
DON'T look at max output of an amplifier when shopping for an amp. It is a marketing scheme that falsly advertises what the amp can do in real life. Look at RMS output per ohm. That is the true output of the amp. (the same rules apply for buying speakers)
DON'T but a prefab box from anywhere online. They rape you on the shipping and you can't get a look at the build quality before hand.
DON'T take shortcuts when wiring up your system (daisy chaining power cables, neglecting fuse holders, leaving exposed wires, not removing paint before grounding a wire to the body.) Doing a system takes time so you might want to get it right the first time so you don't have to redo anything.
DO shop around online retailers. I personally like
www.onlinecarstereo.com, but there are many out there that offer competitive prices and good service.
DO get your wiring done by somebody else if you are not comfortable with something. Most people starting out are worried about breaching the firewall or pulling their carpet up, but it's not that big of a deal. Reserch online and search the site (this site has a lot of info on installing a system in a tib).
and finally... Ask around! You've obvioulsy figured that one out by posting here. Just be careful because there is good info as well as bad info out there. Everybody's got an opinion, but you can generally figure out what's right and wrong with common sense. :3_winkthu