I know from experience here as I have had both the AGX and the GR-2s on my GVR4. First off, the AGXs do ride VERY stiff even on stock GVR4 springs, and I had 2 struts blow out on me quickly with those too... I then switched to GR-2s with the Eibach Sportline's for a 1G DSM, and rode MUCH better even being lowered almost 2 inches... BUT keep in mind if you want to lower the car at all, that the spring perch on the rear strut housing actually sits lower on a 1G strut (which is what you will have to get) so if you use 1G lowering springs with an "even" height all around on a 1g, it WILL sit noticeably lower in the rear. the Sportline's lowered the back of my car too far in my opinion. so know I have the KYB GR-2's with H&R GVR4 specific springs and absolutely love them... the only way I would switch is to coilovers. Especially for a road driven car that you put much of any miles on, I can honestly say that the GR-2/H&R combo is very hard to beat!
Any way, I hope that can give you a little bit of insight into your options, any other questions feel free to ask!
Steve