Based on my experience with the spx-137a's (the older model) you will absolutly need a amp for the components esp if you want them to keep up at all with the subs. I gave them to a friend and they do ok off the stock deck but you can tell they want more power. I ran 75 to them and i'd consider this a minimum. I was running 250 to each side for a while. It had awsome dynamics. You just have to be a bit more careful so you dont accidently get to happy with the vol and blow the speakers.

One sub in that small car would be pretty damn loud. Im not a bass head though.