Absolutely, Jackhammer's a Fast/WIDE SCSI II card for drives of the same kind. IIfx/SCSI2SDv6 is more suited to a fast/NARROW card the likes of the ATTO SEIV in my IIfx. Save Jackhammers for late era Quadras and X100 PPC machines that can make proper us of them. If you're not striping a pair of fast/wide drives for VidCap or the like, you really aren't doing the Jackhammer any justice. YMMV
Two years ago I got a mint boxed IIGS setup (ROM 3 with monitor/1x of each drive) with a large amount of boxed software for $250 (IIc system was included as well). I've been incredibly lazy about setting it up properly unfortunately, so it's still rather stock (High Speed SCSI card and the basic RAM expansion) But I'm picking up a Booti card when they become available!
I originally got a IIgs as a high school graduation present and used it up until I got a SE/30. I don't have my original IIgs, but I've got two now, one of which runs my BBS, so I get to use it to play with it every day! The GS that runs my BBS is equipped with a CFFA3000, ReActiveMicro Transwarp GS v1.1, and Uthernet II card. I also run GS/OS 6.0.4, and have the same HD image running in Sweet16 on my MacBook Pro, so getting files to and from my GS is a breeze.