Fiesta audio

Righteo, I have a MK5 1.25 fiesta and i want to upgrade the speakers in it as they're pretty crap and I can't stand bad sound :P
Anyway i'm pretty sure it can fit 13cm in the front, along with tweeters, of which im not really sure of the size.
I've found these.
I've also been given a sub, don't have a clue about it, just its in my boot, havn't even looked at it yet. Pretty sure they're giving me an amp too.
But what i need to know is, if i bought these speakers, would I get them in easily and would they need an amp or anything?
Biggest post i ever did to explain the smallest of things haha.
any help would be appreciated loads, as you can tell, i have no idea what im talking about :(

someone I know has those speakers.. and they're not really that great. OK though.

Really you're best taking the speaker cover off and measuring the speaker itself, rather than just guessing and being out of pocket with speakers which are too big.. Will be either riveted or screwed into the car.. need to drill the rivets out or you could need a torx screwdriver if they're a star shaped screw head. Tweeters will go in the top of the door card or dashboard.. not sure about the layout in a fiesta.

the sub needs a wiring kit:
- Power cable (connects battery to sub, with fuse included)
- Aux cable (red/white connector, connects sub to headunit)
- Remote start (connects sub to headunit, tells sub when radio is on/off)
- Earth/Ground cable (to stop the sub grounding out)

don't bother trying to remember them, as the wiring kits come as a kit with everything you'll need.. The sub needs an amp (this might be built-in to the sub, you'll have to check) but the speakers don't, unless they're really good speakers in which case they'll come with a crossover.

PS.. you'll need an aftermarket headunit to fit the sub (the speakers will work but sound naff as the power output of standard headunits aren't great) as standard headunits don't have remote start/aux input.

Wow, thanks for the speedy reply! Forgot to mention that the car came with this headunit in it, would that be able to power everything okay?
I can see where the tweeters are which is good I guess :p
Thanks for the advice on the speakers, would you be able to recommend any better ones for around the same price with a maximum budget of around £50? :(
Going to measure the speakers tomorrow to be sure of the size, i've read around on the internet that I should be able to fit 13cm in though :)