My personal view is that I wouldn't bother with SCR, that's what you do if your electronics go down
I would buy a secondhand Inspiration, presently going for £2,500.00 to £3,000.00 and then put an order in for the Vision which is an 11 month waiting list at the moment.
The secondhand units are coming up regularly as the owners Visions arrive, probably the best time to buy a secondhand one, some of them are selling with quite a few extras aswell.
Have a look at
www.rebreatherworld.com