I havn't been around all day...been working in the horseflies and the mud...
Konis pros: adjustable, good firm ride on the road, cons: rallycross will destroy them, pricey
Bilsteins pros: the sherman tank of the shock world, infinately adjustable (if you take them in), ride pretty nice, cons: pricey for a non externally adjustable shock, that's aboot it...I put them on everything I own
KYB GR2's pros:cheap...you can replace them 3 times over for the price of the bilsteins...4 times over for the price of konis, they'll survive OK...the usual upgrade for Subaru people who want a close to OE replacement...a slight step up, cons: cheap, they're not going to ride like the konis do on the road or the bilsteins do on the gravel
Boge Turbogas: pros: eh...not cheap...but not super expensive, upgraded OE spec, cons: nothing spectacular...don't expect anything more than GR2s would get you...but for more money
JVFAB: pros: 50mm Bilstein gravel struts, hardware is welded onto the shock body, if you break them...you're doing it wrong, Vittorio Barres runs them on his open class 4k, cons: nothing really...just about the best gravel suspension you're going to find for our cars, he quoted me $1000 last time I talked to him...which isn't really too bad.
Bottom line: go with either the Bilsteins or the KYBs...you'll cry when your Konis are blown out after their second rallycross from bottoming out too many times.
As for ground control, just don't tell them what you're doing. Just call and ask for 2 sets of 4k rears. Came out to like $400 last time I called them to check.
Oh yea...and don't forget to order new trackdensity strut mounts from 034. I change them every time I take my struts off...stock ones are only good for maybe 20k of normal driving. The 034 ones I'll give maybe 30 or 40k...but with rallycross beatings, they still wear out quick.