Welcome to TBHP ICE, mphsranes!
1) The OHC may not take a 6x7 if you want to retain the stock grilles (on the parcel shelf) and if you don't want to do any cutting of metal. OE provision is for 6.5" speakers. So, going for a GTO637 maybe a better idea. And in any case, if you get a sub, you really don;t need ovals in the back.
2) The 75.4 will drive the 527s and the 637/937 very well!
3) Nothing wrong with getting a GT4-12! That sub is best used in an enclosure anyway (rather than installed on the parcel-shelf in free-air mode). If you're getting a 75.4, it would drive the GT4-12 in a sealed enclosure very well. The sealed box will make sure the bass is tight, so you won't need to worry of the bass-tube-like bass. Believe me, if you feel the bass-tube is too much, you're likely to like the sound of a sub in a sealed box. The advantage is that you don;t need to do any cutting of the parcel-shelf, and you can remove the sub-box when you need (all of the) boot space.
You can get a GT4-12 in a JBL-made box if you go for the CS1204B (GT4-12 in a really nice sealed box from JBL). In any case, if you audition one of those, you'll know what a GT4-12 sounds like, in a properly made enclosure
4) If you plan to get a speaker for the rear, and if you generally do the driving, shall I suggest that you move the fronts (the 527s) to the rear, and get a pair of GTO 607c comps for the front? The 6.5" comps will give much better bass and image in the front. They will really come alive with the 75.4 that you're getting anyway. |