whats the difference btwn the REF6000CS, REF605CS, and KAPPA60.5CS

they all seem to have the same power rating... which ones would you go for? or is there an alternative for £200 ish - 6.5" Comps...

The 6000cs are the replacement for the 605cs. The Kappa 60.5 are the higher quality range (note I say higher not high) Worth looking at JL audio TR and VR ranges.

My 2pence...

6000/605 woofers have a separate ring for mounting and a four bolt X pattern fixing to the speaker itself. Dunno if speaker grilles etc. come with these.

6500/650 woofers are one piece i.e. round. There's also a grille arrangement for surface (visible) mounting.

I have the 650CSE which is 6500s in old money.

Vindaloo.

The speakers with a separate ring are 17cm, which loads of cars have as a standard size, to aid fitting into these cars they supply a mounting ring with all manor of fixing points then the speaker is fitted to that