Should I buy a flat bench or an incline/decline one

I've been lifting weights for around 3 years now yet have never done a bench press of any kind. The reason is that i workout at home with limited equipment. But now I am getting a power cage and bench so i will be able to do benching soon. The question is, should I get a plain ole flat bench or one of those ones that can be adjusted between flat/incline/decline. The flat benches are a lot cheaper and look as if they're sturdier.

Of course it all depends on my goals. Really i'm just looking to get stronger and maybe add some mass. I am not a bodybuilder and am not looking to develop perfectly shaped pecs. So my thinking is that a flat bench will do as I won't be trying to "target" various parts of the pecs by doing inclines and declines.

I also have a full training programme and don't really have time to be incorporating flat, incline and decline bench presses into it.

So basically what I'm asking is - will the flat bench suffice for what i want. Or would I be mad not to get a bench which allows me to do declines and inclines as well. Is it possible that i will find myself "biomechanically unsuited" to the flat bench press and be kicking myself that I don't have an alternative. Also which of the three benches is the "biggest" exercise.

Thanks!