The head unit I had fitted to my Carlton and my first two Omegas, it has MD which I like as they are easy to use.
The speakers I am considering fitting were bought to replace burnt out ones in the 2.0CD, but when I refittedthe original H/U it was unable to drive them. Also the sticky speaker worked a bit better - well enough to sell the car.
They cost me nearly £100 (too much I know) and did sound better than the standard fit in the cars which worked!
That amp is cheap I will be bidding on it tonight.
If there are no rear tweeters (still unsure) I'm going to move the original fronts to the back.
This time I will be mounting the crossovers in the car rather than in the door and running extra cables rather than hacking the original wiring about.
But the Infinitys definately need amping as they stressed my MD head unit quite a bit.
I had been looking at Pioneer amps but I don't know too much about them, I upset a Sony salesman once as I asked if they did amps for grownups as well as the Xplod range - as it all looks suitable for boomy boy racers rather than high sound quality. (They should have released a QS range for the grownups

).
As to subs - more likely to get one for home first if I had a spare £500 but would rather get a new TV or a PS3.
Biggest problem with car subs is where to fit them.