Components in '98 Civic Hatch

Hi! I have an european 1998 Civic Hatch VTi (just like USA hatchs, but with the same engine as the USA Honda Civic Si 98-00). I have a pair of aftermarket 6x9 in the back, a Kenwood headunit (with 20Wx4 RMS), and the original speakers (6 1/2 and tweeters) in the doors. (I think the Civic Si from USA has the same 6 1/2 and tweeters).

Well, i'm about to buy an 800 W 4ch amp (about 100x4 RMS), and I wanted to improve the front speakers (the original 6 1/2s are 15W rms!). Problem is, I don't have too much $$$ to spare, and the options here are not too many (Pioneer, Sony and not much else).
A friend of mine offered me a pair of little-used Pioneer components. The problem is, he only has the crossovers and woofers (with are 50W rms), but not the tweeters.
I have these questions:
Can I use the crossovers and woofers he is offering me, along with the original Honda tweeters? Or are they TOO crappy? I think the results will be better than buying a pair of coaxial 6 1/2s (buying a new set of components is out of the question :(). Any opinions?
Also, where do I mount the crossovers? I guess within the doors, I tried before to run wires from the inside of the car to the doors and is nearly imposible. But, where in the door? Has anyone some pictures or links?

Thanks for your patience and sorry for my BAD english, I live in Argentina.

Nico