The GS is only slightly better than the X1600Pro, so really they're in the same league, and I doubt you'd find the GS low-pro for a small price, the X1600s have been out for a while, and are kind plentiful.
The advantage of the X1600 w/ HDMI is resale you'll likely get much closer to what you paid for it from someone building an HTPC for HD-DVD/BluRay in the future, or you yourself could use it for that.
The nV equivalent is the GF7300 and I haven't seen the HDCP DVI one of those in low pro in retail yet either.
Really it's a tough market, and making the board dual sided for caps regulators, and even memroy, etc, is likely even more expensive than adding a few layers to the PCB design for single side.
I think for now you're stuck with an X1600P, I've sen the low-pro X1600 for under $100, but you're at the whim of supply and demand, and they seem to stick around not much longer than their initial stock sells out. Those things are pretty much a shipment to shipment basis. At least the HDMI has a reason to be always on the list, but the others it would depend on Powercolor and Sapphire etc providing more to people like NewEgg, really for most half-height/Low-pro people the R9500/X300/GF6200/X1300/GF7300 would be 'good enough', and there's a ton of X1300s, just perfect for 2D and light 3D work that these are most commonly used for. Unfortunately, like I said you're going to pay a premium, there's no discount for wanting something outside of the mainstream. Heck the $150 for the HDMi Sapphire is actually at the MSRP, so that's better than what it could be. And really I suspect if the GF7600GS ever do make it that you're loking at at least that $170 you were hoping for, because I think that $50 premium is about what I'd expect on everything due to the niche market and increased costs IMO like I mentioned.