on a tight budget you will do better to spend your first money on some sounddeadening.
Put in into the doors and both sides of the parcel shelf and you might not need to replace the speakers right away.
otherwise, again on a tight budget, if you want more bass from the rear look out for pairs of components for sale with no cross over or tweeters, or some 2ways. if you get 2ways you just clip the little wires to the tweeters. this will keep the important higher range sound in the front where it needs to be.
you can pick up speakers for a fraction of the original value if your canny about it.
I would also recommend putting a plea out on facebook for parts. Its amazing what people have in a cupboard that they will never use again and will send you for postage. you could end up with a sub, amp and matched components just for the want of the question...
The main question is how much cash HAVE you got to throw at car audio right now?
if 100£ then split it down the middle. sounddeadening and secondhand components.
I have a pioneer sub (12'') you can have for £50
some good front speakers and plenty sounddeadening and a sub and you should be good to go.
6th gen Prelude please Mr Honda. RWD 2.4 turbo lude.