ok, i fitted over £2500 of ICE in my a3 r reg the other day. your pre-outs on jvc should be at least about 3-4v. so connect from the non fading to the amp, the a sub to that amp. in terms of ohms, sub and amp have to be the same, ie both 4ohms or both 2ohms, u cant have both different or it could fry your equipment. sorry, i probably didnt read everything thoroughly, but are u planing on just upgrading the existing sub? if u r then dont bother, u r much better off buying say a 12" sub, will sound much better. on my 1.6, the HU connections were standard ISO anyway, so made connecting much easier. yours should b the same. although your head unit may not be iso, my kenwood one wasnt, so u have to have a adapter 2 turn your head unit into iso as well. i am running my rear speakers off the HU, which is 4 x 45 watts and 4v, so more then powerful enough. my front components are running off a amp. if u have a decent sub/amp, then u shouldnt need to turn the gain on the amp more then a 1/4 way up to get it thumping, if u do then somethings wrong. u can get a good 12" sub and amp for under £300. i would recommend a alpine type R sub, i have 2 of those and they are the best ones at that price level.