If you are like myself and want a rack on your sub (because you just like racks), I think you only have the high end models (DSE, 21st, WD) to consider.
I know Alston has a rack, but it has dated technology and a rear mount sway bar that they don't see a need to offer an option on. Most annoyingly, a list of proprietary crossmembers for everything but a T-56. I don't think the Foose Camaros are running them anymore, they mention a "tubular" sub frame in their new literature. I have also read some unflattering comments about flex from a pro builder on Martz frames.
I think there is an opportunity for WD's "new" frame that accepts the DSE conversion stuff, plus a rack in the sub market based on price. I figure that if WD markets his frame for around 2500-2600 with rack and sway bar, it would sell pretty good. Add in 1850 for the DSE stuff and 6-650 for some AFX spindles, you could have a DSE spec, Modified stock sub WITH a rack for 5-5200 w/out brakes? Oh, and fix the single point shear mounts on the back LCAs. How about it WD? Time to update the ol website.
I have been bitching and moaning about the price of DSE's sub, but I would like to eventually buy one after my next deployment. Kyle did mention the possibility of the sub's price increasing if it is very popular. I hope this doesn't happen in the next 6 months or so. I wish they had a lay away plan!