I usually like Cisco gear but the ONS from my experience is not very good.
I would normally do for metro connections Adva and for metro / longer distance Ciena.
Huawei and ZTE also have cheaper options. But... you all can imagine the ‘but’ in this.
I have a tri-state passive DWDM ring. Fiberstore is fine for passive equipment like DWDM muxes. I also use their (re-branded) OEO equipment with custom firmware. I get my DWDM SFP+ from Solid Optics due to repeated compatibility issues with the Fiberstore parts - Solid Optics costs more, but comes with the ability to re-code the optics (in case of a coding issue, or you want to use an optic you bought for Cisco gear in HP gear) and I can re-code them from my cell phone or notebook PC.
Dark fiber around here (NYC area) is reasonably price-competitive with a single 10GbE "lit" circuit between the same 2 endpoints, but you had better be prepared to demand OTDR plots for the link as built, and hold your provider's feet to the fire to fix design / build problems before accepting the circuit. I've seen hairpins with both ends in the same manhole, that add 20+ km distance, extremely poor splices, and lots of other issues. Having a test set that can look at the composite monitoring port and tell you what waves are in use and their optic levels is also important when you're trying to troubleshoot an active circuit (you don't want to take down 40+ channels of traffic to look at something that
might be a problem).
Having said all that, the OP would seem to be better served by getting some extended-range transceivers and having them coded "creatively" if needed - Solid Optics can code an extended-range SFP+ to report itself as a normal optic if needed by the equipment it is installed in.