The 20mm ARB makes an enormous difference, would be much stiffer than the 18mm eibach ones.
The 20mm ones are the extra heavy duty adjustable blade ones only available for the 147 GTA, but they do fit the 156 GTA, I don't know for sure about the SW.
..But if the ARB is shared between the saloon and the SW then it must do I guess.
I got them with the rose jointed drop links like you have on your scooby.
You can't really compare the diameter between different cars (scooby and 156) , its the relative change in the diameter fr the same setup that increases the relative stiffness.
The standard GTA ARB is 16mm, so 20mm represents a 144% increase in stiffness according to the Whiteline docs.
I would say that that is enough, after that I would increase the rear spring rate, something I plan on doing shortly to mine.
I couldn't tell the difference between the quaife and Q2 on track, I drove a few laps in a friends GTA with a quaife at Mondello, and obviously drove Peters Quaife equipped car at the Ring for a few laps.
Both Q2 and quiafe are very good, I would definitely go for the Q2 it seems at least as good as the Quaife.
For out and out track use the AD diff is better, and in the wet infinitely better.
So if you were considering making the car a little more hard-core that would be a possibility, AHM do similar diffs to Ad, and Adie (who has race experience with these and torsen diffs) reckons they are quicker on track.
Also I have let a multi-championship driver loose in my car with the AD diff and then also a month ago with the Q2 diff - he really reckoned the clutch type diff worked better for my car.
Q2 is zero maintenance though, clutch type diffs could need some service I reckon after two years with a lot of track days.
This is an opportunity though to tweak them to a more aggressive setting at the same time..
BTW The AD diffs have new strengthened internals which probably are only relevent for the silly bhp models, but I understand that even the old diffs are fine for the relatively more sensible path you are considering
Jano doesn't reckon a baffled sump is needed, I don't have one, and haven't heard any experienced mechanics recommendations that one is needed.
Type-R tyres don't generate the same grip as full race slicks anyway, about 1.3g is the max for non cambered corners.
I have never had a low oil pressure warning on track.
The 3.7 with TBs possibly does run a little hot for slow very windy tracks and possibly could do with a bigger oil cooler, or upgraded radiator. It isn't an issue on typical tracks that have some high speed sections that ram air into the engine.
I don't know if the S/C only option has the same issue, I suspect not.
The 147 GTA has a larger oil cooler, and is a mod that I will consider at some point, although maybe try a fancier core radiator first.
I think the adjustable AD sportline corses are superb, and a very significant improvement over the non-adjust AD kit which is perhaps hard-wired a bit towords comfort for British speeds, but reports have come back that for very high speeds its under damped.
The Corses are aluminium and have external reservoirs, plus are based on Intrax ones which have a good rep.
40 settings for adjustment (coupled bound/rebund), and only takes a few seconds each corner to do so.
Not sure the KW's allow adjuatment of bound and rebound, even in a coupled fashion?
(Think it is just one paramater?)
I can compare mostly for track use with Peters setup for his hybrid, which felt very impressive too.
I would say that Peters car was setup very well as an allrounder for road/track, but when you were in my car I would have had the rear dampers set up max - which obviously would make the car edgier and veery firm.
So don't think you have to have your teeth rattled all the time
The extra damping is really appreciated when you use proper type-R tyres and works very well with the stiffer ARB to allow the back to move slightly on tracks that you can really commit on. The Corse damping can be configured to be so strong it would even cope with slicks okay I suspect.
I have AD 10kg front linear springs over the AD default of 8Kg.
In retrospect this is too firm, the car doens't need that rate.
8Kg or 9kg would be fine, I intially had 8kgs
Making the springs too stiff at the front adds stability but also some understeer, 8Kg is very comfortable, but I think 9kg might be a good balance.
I have set of 9kg fronts that I haven't actually tried yet.
For the rear I have standard 4.5Kg + 40% wide progressive AD springs, possibly made by intrax.
These are very comfortable for the road due to their progressive nature, but I would recommend a slightly stiffer setup, which I am investigating myself currently.
Jano mentioned that they are working on newer more sporty spring rates, I'll check up on the status of that soon.
Personally its probable that I will actually go for much more extreme linear rear springs (maybe even 10kg) to get the car to oversteer more.
These probably aren't what you would need though since your car would have more family commitments I suspect, and I'm letting my get a little more hard core as it ages
I reckon the S/C conversion is better bang per buck with a lot more torque with the high spec "evo" fuel injector option
(340bhp or so I believe claimed now, the AD website is out of date with 320bhp shown which refers to the old kit before they got more advanced injectors).
The 3.7 is a purer creation and sounds better though.
In your scenario I suspect I would go for the 3.7 with TBs if money really was no object (the TBs are an expensive extra though.. ).
The noise will raise the cackles on the back of your neck in a way the s/c scream won't.
Moneywise though, the s/c option is the sensible one
Hell money is no object right, I forgot the 400bhp N/A option, okay I would go for that
I don't know how much it costs fitted..