As you would have guessed if you had read other threads i have posted in about vibe stuff, i am anything but a fan - IMO STAY AWAY
The infinity comps are good, ive also heard v good things about crystal comps (for clear sq). Ive got some polk momo, very good set IMO. Ive also heard allot of good stuff for the dls a5s
Defo amp the fronts wount be running anywere near full potentail if run off HU.
IMO front get a mac attack 4075 or 4050(i think its this) and bridge 2 channles for each front speaker, leaves you room to expand to go active on fronts - good amp on specails at
http://www.caraudiodirect.co.ukwww.caraudiodirect.co.uk
Get another 2 channel amp for the sub, then get a 4ohm sub and run it bridged - you could get anopther mac attack to make it look consistent.
Sub, not too hot on - you going for sq or spl? but 1 decent powered sub should do - get a 10" if its faster bass, dance music trance ect but it wount drop as low, a 12" will drop lower but is slower, so better for hip hop ect.
IMO you don;t really need rear fill, if you want it, does you car have stock rears?? if so leave them in there run off HU
Defo an alpine HU for front the 7894rb is exclecnt i have one and LOVE it, old stock though can get it for £275 (rrp was 500) form
http://www.mcs-direct.co.ukwww.mcs-direct.co.uk )
SO IMO
hu - 7894rb - £275
http://www.mcs-direct.co.ukwww.mcs-direct.co.uk
Comps - dls/cystals - £160/£200(IIRC)
http://www.caraudiodirect.co.uk/www.caraudiodirect.co.uk
AMPS - mac attack 4075 and 2050(or something) - check
http://www.caraudiodirect.co.ukwww.caraudiodirect.co.uk for prices
Sub - not sure
but it depends how good a system, as you could go into crossovers, eqs, line drivers ect ect
then you have the boot build materials, wiring, sound proofing
HTH
Rorrie